Nervous system| Type| function| classification| structure| characters|

  NERVE FIBRE  

A nerve fiber is a cord like structure containing bundles of axons in the peripheral nervous system. It provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs. Within a nerve, each axon is surrounded by a layer of connective tissue called endoneurium. The axons are bundled together into groups called fascicles and each fascicle is wrapped in layer of connective tissue called Perineurium. Finally, the entire nerve is wrapped in a layer of connective tissue called epineurium. Nerves are bundled along with blood vessels since the neurons are of a nerve have fairly high energy requirements. A blood vessel carrying blood to a nerve is known as vasal nervosa. Within the endoneurium, the individual nerve fibers are surrounded by a low protein liquid called endo neural fluid.it constitutes a blood nerve barrier similar to the blood brain barrier. Molecules are thus prevented from crossing the blood into the endo neural fluid. During the development of nerve oedema (swelling)due to nerve injury, the amount of epineural fluid may increase at the site of injury. This can be visualized using magnetic resonance neurography.

Histologically nerves are of two kinds:

✒ MYELINATED NERVE FIBRE: -

The nerve fiber which are surrounded by a lipid rich insulating layer, so it appears white called myelin sheath. Myelin sheath is an electrical insulator, its purpose is to speed the transmission of nerve impulse. A neuron having myelin sheath means faster conduction, faster transmission and faster transfer of nerve impulses. Myelin sheath is interrupted at some places; these are called nodes of Ranvier, which is always constant in number. The space between two nodes of Ranvier is called internode. Speed of conduction of nerve impulse is faster in myelinated fiber. These nerves are more than 1µ in diameter.

✒NON-MYELINATED NERVE FIBRE: -

Nerve fibers without myelin sheath are, called non-myelinated nerve fibers. In non-myelinated nerve fibers, nodes of Ranvier are absent. They appear grey because of the absence of myelin sheath: post ganglionic sympathetic nerves are non-modulated. The nerve fibers, which carry nerve impulse from receptor organs to the central nervous system are, called afferent nerve fibers or sensory neurons. The nerve fibers, which carry nerve impulse from the central nervous system to effecter organs are, called efferent nerve fibers or motor neurons. The nerve fiber that contains, both afferent and efferent axons and thus conduct both incoming sensory information and outgoing muscle commands in the same bundle.

Types of Neurons 

The nerve cells have been classified either on the basis of their structure or function as follows: - 

✅Functional type of Neurons: On the basis of their functional or their physiological properties, the neurons may be divided into following types: -

✔Sensory or afferent neurons: These neurons carry a stimulus from the peripheral or visceral receptors to the central nervous system.

✔Motor or Efferent Neurons: These neurons carry impulses away from CNS to the 

effectors like muscles and glands. 

✔Neurosecretory neurons: These cells are specialized for producing neurohormones. 

✔Internuncial neurons: These are generally located in the central nervous system and serve to link the sensory and motor neurons.

✅Structural classification of neurons 

✔Multipolar Neurons: -

These neurons have an axon and many dendrites. Examples of multipolar neurons are motor neurons and inter neurons found in brain and spinal cord. 

 ✔Bipolar Neurons: - 

When one axon and one dendrite arise from one soma i.e. they have an axon and a dendrite. The bipolar neurons are found in retina and in the ganglia of VIII nerve. 

✔Unipolar or Pseudo unipolar Neurons: -

All developing neuroblast cells pass through a stage in which they have only one process the axon. During the later development it may be divided into two processes, one terminating in the central nervous system while another moves out. The unipolar neurons are found in the posterior roots of spinal nerves, in the mesencephalic nucleus of V cranial nerve and in the nerve roots of IX and X cranial nerve. 

✔Non-polar Neurons: -  

When many processes arise from the soma and all are equal without any distinction of axon or dendron, the neuron is called non-polar neuron. These nerve cells are unpolarized and cannot be differentiated into dendrites and axon. In non-polar neurons, nerve impulse can be conducted in any direction. Non-polar neurons are found in nerve net of coelenterates.

NEUROTRANSMITTERS 

Neurotransmitters are the endogenous chemical messengers that enable neurotransmission liberated at the nerve ending. They transmit signals across a chemical synapse from one neuron (nerve cell) to another target neuron a, muscle cell, or a gland cell. They play an important role in shaping everyday life and functions. 

✅Types of neurotransmitters: -

There are about 40 neurotransmitters and they have been classified into two types: - 

✔Rapidly acting neurotransmitters

✔Slowly acting neurotransmitters 

✅Rapidly acting neurotransmitters are small molecules and cause acute response. 

 It includes: -

i) Acetylcholine 

ii) Amines: Norepinephrine, epinephrine (Catecholamines), Dopamine, Serotonin.

iii) Amino acids like GABA (glycine and gamma amino butyric acid), glutamate, aspirate 

✅Slowly acting neurotransmitters are neuropeptides having prolonged effect: - 

It includes: -

✔Neuroactive peptides which are releasing hormones secreted by hypothalamus, for eg. TRH, LH, somatostatin 

✔Pituitary peptides like ACTH, vasopressin, oxytocin, endorphins 

✔ Peptides acting on gut and brain like leucin, methionine, cholecystokinin, neurotensin, insulin, and glucagon. 

✔ Neuropeptides from other tissues like angiotensin-II, bradykinin, and bombesin.

Excretory system| Nephrons| Micturition| Loop of Henle| Ultra filtration| -Learning hub

 EXCRETORY SYSTEM 

The following steps are involved in the excretory system.

STRUCTURE OF VERTEBRATE KIDNEY: -

The main excretory organs of vertebrates are kidney. Kidneys are mesodermal in origin. Each adult kidney is composed of a number of structural and functional units called nephrons or, nephric tubules or the uriniferous tubules. Basically, there are three types of kidneys met within the vertebrates. 

(i) Pronephros: It is the embryonic kidney of all vertebrates except Myxine and Belladona, it is the head kidney that remains functional in the larvae of cyclostomes, fishes and amphibians but later degenerates 

(ii) Mesonephros: It is the opisthonephric kidney of adult cyclostomes, fishes and amphibians and also serves to be the embryonic excretory organ in amniotes. 

(iii) Metanephros: It is the functional kidney of the adult, reptiles, birds, mammals and man. The detailed study of metanephric kidney is discussed below.

✅In man, the two kidneys lie behind the peritoneum on either side of the vertebral column extending from 12th thoracic to 3rdlumbar vertebrae. In man and most mammals, the left kidney is usually a little higher than the right kidney, reaching the level of the eleventh rib. In healthy man, each dark red bean shaped kidney weighs between 120-170 gms and measures from 11-13 cm in length. Each kidney is covered by a layer of fibrous connective tissue, called renal capsule.

✅The physiological anatomy reveals that each kidney comprises about 1.2 million nephric tubules or nephrons, functional unit of kidney. Each nephron is 4–5 cm. long. It is divisible into an outer granular cortex and inner paler medulla. Hilus is the inner medial border of the kidney which is somewhat concave and has an indentation through which passes the renal arteries, veins, nerves and the lymphatics, the pelvis or the ureter.

✅The funnel shaped upper end of pelvis is formed by the joining together of about three or four major calyces each of which is intern made up of several short branches or minor calyces. The medulla of kidney comprises of some ten to fifteen pyramids which project into the calyces and separated by the renal columns of Bertini.

Structure of single nephron: - 

The renal tubule or nephron was first described by Marcello Maiphigi (1666) and later by Bowman (1842). Approximately 2.2million nephrons are present in both kidneys i.e., (1.1 million in each kidney). In an adult person, a single nephron measures about 5-6 cm and is divisible into two parts.

1) Malpighian or renal corpuscle 

2) Renal tubule.

(1) Malpighian or renal corpuscle: Each nephric tubule begins as a blind dilated cup shaped sac called Bowman’s capsule. It is double layered and situated in the cortex of kidney. The Bowman’s capsule is invaginated by a tuft of some 40-50capillary loops, each covered by special epithelial cells known as Podocytes. Podocytes have slit pores through which ultra-filtration occurs and forms the Glomerulus. The glomerular capillary tuft surrounded by its capsule is termed as Malpighian corpuscle. Blood enters the capsule through afferent renal arteriole and after passing through glomerular capillary network it is collected by the efferent renal arteriole. 

(2) Renal tubule: The long portion of the nephron following the Bowman’s capsule is termed as renal tubule. It is divided into the following regions.

✅ The proximal convoluted tubule, 

✅The loop of Henle (Descending limb and ascending limb) 

✅ The distal convoluted tubule 

✅Collecting duct 

• PCT: The proximal convoluted tubule lumen of which is continuous with Bowman’s capsule is about 12-24mm in length lies in the cortex of kidney. It consists of large columnar cells with a brush border produced into numerous microvilli of 1 to 4mµ in size. 

• The loop of Henle: It is a hair pin-shaped part of nephron after PCT. The loop of Henle consists of one descending limb and one ascending limb Descending limb of loop of Henle is permeable for water and is impermeable for salts while ascending limb of loop of Henle is impermeable for water. Ascending limb of loop of Henle is called diluting segment of nephron.

• DCT: The next part of nephron that is again highly convoluted is, called distal convoluted tubule (DCT). It lies in renal cortex. It is made up of cuboidal epithelial cells but have few scattered microvilli. DCT opens into collecting tubule. 

✅Collecting tubule (CT): All collecting tubules receive many functional tubules from other nephrons and finally open into the renal pelvis as the papillary duct of Bertinii. 

✅Types of nephrons in mammalian kidney 

(a) Cortical Nephrons: -

The nephrons situated in cortical region are, called cortical nephrons. In cortical nephrons, loop of Henle is short. In a kidney 15 to 35% nephrons are cortical nephrons. 

(b) Juxtamedullary nephrons: -

Nephrons situated near medulla part are, called juxtamedullary nephrons. It is formed by the DCT and glomerular afferent arteriole. It is so named because it lies next (juxta)to the glomerular. In juxtamedullary nephrons, loop of Henle is long and parallel blood vessels, called vasa recta are present. In a kidney 65 to 85% nephrons are juxtamedullary nephrons. It works only in condition of stress.

It consists of three types of cells. 

(1) The macula dense, a part of the distal convoluted tubule of the same nephron. It acts as a chemoreceptor and are stimulated by decreased NaCl concentration and thereby cause release of rennin.

(2) Juxtaglomerular cells or granular cells which secrete rennin. These cells are smooth muscle cells of afferent arteriole which supply blood to the glomerulus. They are baroreceptors and respond to changes in the pressure gradient. They are innervated by sympathetic nerves. 

(3). Extraglomerular mesangial cells (Laci’s cells) These cells are located at the junction. between afferent and efferent arterioles. They are contractile and play a role in regulation of GFR. 

MECHANISM OF RENAL EXCRETION (URINE FORMATION): -

As mentioned above, kidneys are the chief organs of nitrogen excretion invertebrates. Each minute, the two kidneys filter approximately 1200 ml of blood to collect 125 ml of filtrate and form about 1 to 2 ml of urine (per minute) and thus eliminate extra water, nitrogenous wastes and inorganic salts from the body. The entire mechanism of renal excretion involves three main steps. 

• Ultra filtration 

• Selective reabsorption 

• Tubular secretion 

(A) Ultra-Filtration: -

Described first by Ludwig (1844) and later modified by Richards (1942), the ultra-filtration or glomerular filtration is the first step in urine formation. The glomerular capillaries receive the renal blood supply through afferent renal arteriole which form a high-pressure bed in glomerulus, and it is approximately 60 mm Hg (Guyton,2003). Opposing the effects of blood pressure in the glomerulus are- 

(1) Colloidal osmotic pressure of plasma proteins 

(2) Tubular pressure of the Bowman's capsule itself, which are approximately 32 mm Hg and 18 mm Hg, respectively. Thus, in the Bowman's capsule a blood pressure of about 60 mm Hg is being opposed by an internal pressure of approximately 50 mm Hg (colloidal osmotic pressure plus the tubular pressure) and this spares a filtration pressure of about 10 mm Hg (called the net filtration pressure) which is sufficient to cause filtration of the non-protein substances of plasma across the glomerulus (fig. 4.6). Everything except plasma proteins is filtered and the fluid collected is called ultrafiltrate. The total amount of glomerular filtrate formed each minute in all the nephrons of both kidneys is known as the glomerular filtration rate. It is approximately 125 ml/min or 180 liters/day.

Filtration Coefficient (Kf) is defined as total amount of ultra-filtrate formed by all the nephrons of both kidneys per minute per 1mm of Hg of net Filtration pressure. 

Kf = 125/10 = 12.5 ml/min/mm of Hg 

Another noteworthy feature of ultrafiltration is the tremendous permeability of the glomerular capillary membrane which is several hundred times higher than any capillary membrane inhuman body. Histologically it is made up of three layers:

(1) endothelium of the capillary, 

(2) basement membrane, and 

(3) A layer of epithelial cells that line the surface of Bowman's capsule. The fenestrae and slit pores of these layers increase permeability but prevent the filtration of all particles having an average diameter greater than 70 A. Since plasma proteins are slightly larger than 70 Aº diameter, it is possible for the glomerular membrane to prevent the filtration of all those substance with molecular weight equal to or higher than those of the plasma proteins.

✅Factor affecting Glomerular Filtration Rate (GFR) 

Any change in any of these pressures affects GFR. 

✔ When the blood pressure in the glomerulus raises GFR increases. 

✔ When colloidal osmotic pressure (CPO) increases, GFR decreases provided other two factors are constant (COP decreases in starvation and due to under nutrition). 

✔ When the tubular pressure in the Bowman's capsule increases, GFR decreases. 

✔ Increase in blood volume increases GFR. 

✔ Increase in cardiac output increases GFR.

✔ Decrease in the number of functional nephrons will decrease GFR (Some nephrons become non-functional due to old age). 

✔ Sympathetic discharge will produce constriction in afferent arteriole and this decreases GFR.

 Determination of GFR: -

GFR is taken as one of the kidney function tests. By quantifying GFR one can understand how the kidney handles various substances. Thus, substances with excretory rate less than filtration rate must undergo tubular reabsorption whereas substances with excretion rate more than filtration rate must undergo secretion. 

✅Clearance Test: - 

The clearance of a substance may be defined as the concentration of that substance in plasma same as in glomerular filtration and is neither reabsorb nor secreted by the tubular epithelium. It is a measure of the rate of glomerular filtration. Inulin, a polymer of fructose found in the roots of certain plants is easily filtered, it is neither reabsorbed nor secreted and has a clearance equal to GFR. 

✅Transport Maximum (Tm): -

Another parameter of renal excretory function is the transport maximum which is the maximum ability of the kidney either to reabsorb or secrete a given material. For example, Tm of glucose is defined as the maximum amount of glucose that can be reabsorbed by all nephrons of both the kidneys per minute. Average TmG = 360 mg/min (320 mg/min in females and 375 mg/min in males). If the tubular load of glucose becomes 400 mg then it will be excreted in urine at the rate of 40 mg/min. When tubular load of glucose is less than TmG then no glucose is lost in urine.

Glucose lost in urine = tubular load of glucose - TmG 

= 400-360 

= 40 mg/min

(B). Selective reabsorption: -

 The filtered fluid in the Bowman's capsule and in the tubule is called the glomerular filtrate. It has almost the same composition as the fluid that filters from the arterial end of capillaries into the interstitial fluids. The glomerular filtrate has no red blood cells but consists of about 0.03 percent proteins, a great amount of glucose, salts, nitrogenous end-products and water. About 99 percent of the water and almost all other useful substances present in the glomerular filtrate are to be reabsorbed back into the blood as the filtrate passes through various parts of the convoluted tubule. 

✅ Reabsorption in the proximal convoluted tubule 

About 65 to 80 percent of the glomerular filtrate is reabsorbed in the proximal convoluted tubule and this fraction is referred to as the obligatory reabsorption. The epithelial cells of the proximal tubule have a brush border composed of thousands of very minute microvilli which facilitate a rapid and active diffusion of sodium from the peritubular capillary blood. Each time a positively charged sodium ion is pumped out of the tubule, a negatively charged ion follows it and it is usually a chloride ion which thus leaves the tubule, since it is the most abundant negatively charged ion in the tubular fluid. 

The peritubular capillary bed has a mean blood pressure of about 13 mm Hg which is slightly higher than the filtration pressure. The peritubular fluid now has a higher osmotic pressure because of an increased concentration. Both these factors influence the movement of water from the filtrate which also carries away, passively, substance like glucose, amino acids, and potassium, calcium and phosphate ions from the filtrate.

✅ Reabsorption in the loop of Henle 

At the end of proximal tubule, the fluid is almost isotonic with blood. In the rest of its course, it is converted into urine of the appropriate concentration through a complicated sequence of events termed as the counter-current mechanism. The mechanism is basically associated with the anatomy of the loop of Henle which is a hair-pin loop between the proximal and distal convoluted tubules of nephrons. Entire mechanism of the counter-current system is as follows: 

(a) The ascending limb of loop of Henle with thicker walls is impermeable to water but actively transports sodium and chloride ions passively from the tubular wall into the renal medulla. This causes an increase in the osmolarity of the interstitial fluid in the medulla. 

(b) The increase in the osmolarity due to the sodium pump causes water to leave the thin-walled descending limb. This makes the filtrate increasingly hypertonic as it proceeds from the renal cortex towards the papilla. 

(c) The Na+ secreted by the cells of the ascending limb of the loop of Henle into the interstitial fluid escape passively into the adjacent blood vessels or the descending limb of the loop following a concentration gradient. 

(d) Thus, by this re transport of the sodium (and chloride) again and again the counter-current multiplier mechanism increases the concentration of sodium chloride in the medulla, and consequently determines the concentration of urine.

(3) Reabsorption in the distal convoluted tubule: -

The fluid reaching the distal tubule of the nephron is hypotonic and it is the antidiuretic hormone (ADH) from the hypothalamic pituitary which now controls the concentration of the urine. This ADH controlled water reabsorption is the distal and collection tubule is termed as facultative reabsorption, and its mechanism is simple. In water diuresis very little ADH is present in the blood, so the distal and collecting tubules become relatively impermeable to water and a dilute urine is excreted but when the body has little water (or say when the blood is more concentrated) a larger amount of ADH is present in the blood and the kidneys conserve more water because of tubular reabsorption Hence the urine becomes concentrated. Mechanism of urine formation in mammal.

✅Tubular Secretion: -

Tubular secretion is the final step in the urine formation. The epithelial lining of the tubule is able to collect electrolytes and water from the fluid but at the same time many foreign substances are readily secreted by the tubule. It is believed that some creatinine, potassium, phenol red, H ion and penicillin are the main substances secreted by the tubular epithelium in man. 

✅Composition and characteristics of urine: -

The concentrated fluid entering the collecting tubule is called Urine. Through the way of pelvis and ureters, it is usually stored in the urinary bladder and is discharged from the body from time to time. The normal volume and composition of urine varies widely from day to day and is being governed by, among other things, the type of food and fluid taken and the amount of fluid lossby other agencies, a factor which itself depends upon environmental temperature, humidity, exercise and sweating etc. 

Micturition: -

Micturition is the mechanism by which the urinary bladder empties itself when it becomes filled with the urine. The urine is basically collected in the pelvis of the kidney where all the nephrons of a kidney open through their collecting tubules. As urine collects in the pelvis, its pressure increases and initiates peristaltic waves occurring every 10 sec or so and travelling through the ureters at a velocity of about 3.0 cm/sec and pushing a little spurt of urine into the bladder, the stretch receptors located in the bladder wall and proximal urethra become stimulated creating a micturition reflex. The detrusor muscles, which make-up the body of urinary bladder, contract during the micturition reflex; the internal sphincter of the urethral opening relaxes and the urine  is evacuated.

Reproductive health; problems and strategies| Population explosion| Birth control methods|

  Reproductive Health: Problems and Strategies 

Reproductive Health simply refers to healthy reproductive organs with normal functions. According to the World Health Organization (WHO), reproductive health means a total well-being in all aspects of reproduction, i.e., physical, emotional, behavioral and social. The improved reproductive health of society requires following factors. 

✔ Better awareness about sex-related matters. 

✔ Increased number of medically assisted deliveries and better postnatal care so, as to decrease maternal and infant mortality rates. 

✔ Increased number of couples with small families. 

✔ Better detection and cure of STDs (Sexually Transmitted Diseases). 

✔ Overall increased medical facilities for all sex-related problems. 

✒Awareness of Reproductive Health: -

Some of the measures taken for the awareness of reproductive health are as follows: -

(i) The family planning programmes were initiated in India in 1951 and were periodically assessed over the past decades. The programmes were improved and covered reproduction-related areas under the popular name Reproductive and Child Healthcare (RCH) programmes. It was launched in 1997. Major tasks of RCH programme are: -

✅Creating awareness among the people about reproduction related aspects. 

✅ Providing facilities and support for building up a reproductively healthy society. Governmental and non-governmental agencies have taken various important steps to create awareness among people about reproduction-related aspects. 

(ii) In schools, introducing sex education is a good step to provide right information to adolescents to discourage them from believing in myths and misconceptions about sex-related issues. Adolescents should be informed about reproductive organs, adolescence and related changes, safe and hygienic sexual practices, sex abuse, STDs, AIDS, etc.

 (iii) Married couple or those in marriageable age group should be educated about available birth control options, care of pregnant mothers, postnatal care of the mother and child, importance of breast feeding, equal opportunities for the male and female child, etc. This will lead to the formation of socially conscious healthy families of desired size. 

(iv) Successful implementation of action plans like providing medical assistance and care to reproduction-related problems, pregnancy, delivery, STDs, abortions, contraception, menstrual problems, infertility, etc. need strong support and infrastructural facilities.

(v) Statutory ban on amniocentesis It is a prenatal diagnostic technique based on chromosomal pattern in which a sample of amniotic fluid is taken from the uterus of a pregnant woman to detect the early development of foetus. The benefits of amniocentesis include the diagnosis of chromosomal abnormalities and developmental disorders of it foetus. However, is being misused for sex-determination of foetus that leads to female foeticides. Therefore, statutory ban on for amniocentesis sex-determination keeps check on female foeticides. 

Population Explosion: -

The tremendous increase in the size and growth rate of population is called population explosion. It occurs due to increased health better living conditions.

(i) Reasons of population explosion include 

✅ Decreased death rate. 

✅ Declined Maternal Mortality Ratee (MMR). 

✅ Decreased Infant Mortality Rate (IMR). 

✅Increase in the number of people in reproductive age. 

(ii) According to the 2001 census report, the population growth rate was around 1.7%, i.e. 17/1000/year. By this rate, our population could double in 33 years. 

Methods to prevent population explosion include 

✔ Raising the marriageable age now, it is 18 years for females and 21 years for males. 

✔ Couples with small families should be given some incentives. 

✔ Birth control is an important step to control the population growth by motivating smaller families by using contraceptive methods. 

Birth Control (Contraception) Methods: - 

Contraceptive methods are ideal if they are user friendly, easily available, effective, reversible with no side effects and non-interferring with the sexual drive, desire and the sexual act. There are several methods of birth control that can be categorised as follows: - 

Natural Methods: -

Natural method of birth control involves avoiding ances of sperm and ovum meeting. It can be achieved by 

•  Periodic abstinence in which couples avoid coitus from day 10-17 (fertile period) of the menstrual cycle. In this period, ovulation 1s expected to occur and chances of fertilization are very high. This method is also called rhythm method. 
•  Coitus interruptus is also called 'rejected Sexual intercourse' or 'pull-out'/withdrawl method. In this method, the penis is withdrawn from the vagina just before ejaculation, so that semen is not deposited in the vagina.

• Lactational amenorrhea is the absence of menstruation during the period of intense lactation following parturition. As ovulation does not occur in this period, the chances of conception are nil. This method is reliable for a maximum period of 6 months after delivery. Main advantage of these methods is that, they do not cause any type of side effect. The main disadvantage is that, these methods are not 100% reliable, as these depend on chance. 

Barrier Methods: -

These methods are based on the prevention of ovum and sperm from physically meeting with the help of barriers. Barriers may be mechanical or chemical and uscd by both males and females 

(i) Mechanical Barriers: -

✅Condoms:-

 They are made of thin rubber or latex sheath to cover the penis in male or vagina and cervix in females (femidom) They prevent meeting of sperm and ova. Condoms provide protection from sexually transmitted discases. They are disposable and can be self-inserted and thereby gives privacy to the user. 

✅Diaphragms, Cervical Caps and Vaults: - They are made up of rubber that are inserted into the female reproductive tract to cover the cervix during coitus. They are reusable. 

(ii) Chemical Barriers: -

They include spermicidal creams, jellies and foams. They are usually used along with the barriers to increase their contraceptive efficiency.

Intra Uterine Devices (IUDS): - 

These devices are introduced in the uterus through vagina by doctors or expert nurses. These are of following types: -

✅Non-medicated IUDs, e.g. Lippes loop. 

✅ Copper-releasing IUDs, e g. Cu-T, Cu-7 and multiload 375. 

✅ Hormone-releasing IUDs, e.g. progestasert, LNG-20.

IUDs prevent contraception in the following ways: -

✅ Increase phagocytosis of sperms within the uterus. 

✅ Some IUDs suppress sperm motility and fertilizing ability of sperm by releasing copper ions. 

✅The hormone releasing IUDs make uterus unsuitable for implantation and make the cervix hostile to sperms. IUDs are ideal Contraceptives for females who want to delay pregnancy. It is one of the most widely accepted contraception method in India.

Oral Contraceptives: -

These are hormonal preparations in the form of pills. Their major fecatures include 

(i) Pills are of two types-combined pills and mini pills. Combined pills (Mala-D and Mala-N) contain synthetic progesterone and oestrogen whereas mini pills contain progestin (progesterone like synthetic hormone) only. 

(ii) Oral pills inhibit ovulation and modify the quality of cervical mucus to prevent/retard the entry of sperms. They also modify uterine endometrium by making it unsuitable for implantation. 

(iii) Oral pills have to be taken daily for a period of 21 days starting within the first five days of menstrual cycle. 

(iv) Saheli an oral contraceptive pill developed by scientists at Central Drug Research Institute (CDRI), Lucknow, contains a non-steroid called centchroman. It is a once-a-week pill, with very few side effects and high contraceptive value. 

Implants or injections: -

These are effective for longer period, although their mode of action is similar to thal of oral contraceptives. Progesterone alone or in combination with oestrogen are used by females as injections (Depo Provera) or implants under the skin. 

Emergency Contraceptives: -

It includes administration of high dose of progesterone or progestogen-Oestrogen Combinations within 72 hours of coitus. It has been found to be very effective to avoid possible pregnancy due to unprotected intercourse.

Sterilisation or Surgical Methods: -

Sterilisation methods are used by male/female partner as a terminal/ permanent/stable method to prevent any more pregnancies. These methods block the transport of gametes and prevent Contraception. There are of following two types 

(i) Vasectomy is applied in case of males. In this method, a small portion of vas deferens is removed or tied up through an incision on the scrotum to prevent the passage of sperms.

 

(ii) Tubectomy is applied in case of females, where a small part of Fallopian tube is removed or tied up through a small incision in the abdomen or through vagina to prevent the passage of ova. Both of these methods are highly effective. but poorly reversible. 

Spermatogenesis | Sperm | Oogenesis | Menstrual cycle |

  Gametogenesis  

It is the process of producing haploid gametes from diploid germ cells in the gonads, i.e. sperms and ova are produced in the testis and ovary, respectively. It is of the following two types (7) Spermatogenesis (17) Oogenesis 

💥Spermatogenesis: -

It is the production of sperms in males. 

(i), In tastes the immature male germ cells (spermatogonia) produce sperms by spermatogenesis that begins at puberty. 

(ii) Spermatogonia (sing. spermatogonium) present on the inside wall of seminiferous tubules multiply by mitotic division and increase in numbers.

(iii) Each spermatogonium is diploid and contains 46 chromosomes. Some of the spermatogonia called primary spermatocytes periodically undergo meiosis. 

(iv) The primary spermatocytes undergo first meiotic division leading to two equal, haploid cells called secondary spermatocytes, which contains only 23 chromosomes each.

(v)The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid spermatids which contain only 23 chromosomes each.

(vi) The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis. Thus, each sperm too contains only 23 chromosomes.

(vii) Sperm heads are embedded in the Sertoli cells and are finally released from the seminiferous tubules by the process called spermiation.

Role of Hormones in Spermatogenesis: -

The following hormones play an essential role in spermatogenesis.

(i) Spermatogenesis starts during puberty with the significant increase in hypothalamic hormone called Gonadotropin Releasing Hormone (GnRH). 

(ii) The increased level of GnRH acts on the anterior pituitary gland and stimulates the secretion of two gonadotropins, i.e., LH (Luteinizing Hormone) and FSH (Follicle stimulating Hormone) 

(iii) LH acts on the Leydig cells and stimulates the synthesis and secretion of androgens, which in turn stimulate the process of spermatogenes1s. 

(iv) FSH acts on Sertoli cells and stimulates the secretion of some factors, which help in the process of spermiogenesis.

💥Structure of a Sperm: -

(i) A sperm is composed of a head, neck, a middle piece and a tail. 

(ii) A plasma membrane encloses the whole body of sperm. 

(ii) Head contains an elongated haploid nucleus, the anterior portion of which is covered by a cap-like structure called acrosome. 

(iv) The acrosome is filled with enzymes that help in fertilization of the ovum. 

(v) Neck contains two centrioles, a proximal centriole, which is necessary for first cleavage division of zygote and a distal centriole, that gives rise to axial filament of tail. 

(vi) Middle piece possesses many mitochondria to produce energy for the movement of tail to facilitate sperm motility. 

(vii) Tail of the sperm consists of an axial filament. It helps in the movement of sperm inside the female reproductive tract towards the ovum for fertilization.

0ogenesis: -

It is the process of formation of a female gamete or ova in the ovary. 

(i) It starts during embryonic stage in a female. 

(ii) About a million oogonia are formed in the ovary of the female fetus which is 25 weeks old. No new oogonia are formed after birth.

(iii) The oogonial cells start meiotic division, enter into prophase I, get temporarily arrested at that stage and are called as primary oocytes.

(iv) Each primary oocyte then gets surrounded by a layer of granulosa cells called primary follicle.

(v) A large number of primary follicles degenerate during the phase from birth to puberty. As a result, about 60,000-80,000 primary follicles are left in each ovary at puberty.

(vi) The primary follicles get surrounded by more layers of granulosa cells and a new theca and are called secondary follicles.

 

(vii) The thecal layer in secondary follicles becomes organized into an outer theca externa and an inner theca interna. This stage is called tertiary follicle. 

(viii) Tertiary follicle is characterized by a fluid-filled cavity called antrum. 

(ix) At this stage, the primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. 

(x) The first meiotic division, which is unequal results in the formation of haploid secondary oocyte and tiny first polar body. 

(xi) Secondary oocyte retains bulk of the nutrient rich cytoplasm of the primary oocyte. 

(xii) The tertiary follicle develops into a mature follicle or Graafian follicle. 

(xiii) The secondary oocyte forms a new membrane called zona pellucida surrounding it.

(xiv) The Graafian follicle ruptures to release the secondary oocyte (ovum from the ovary by the process called ovulation.

Ovum: -

Human egg or ovum is non-cleidoic (i.e. without shell), alecithal (i.e. yolk is absent), microscopic with about 0.1 -0.13 mm or 100-130 um diameter. The ovum possesses three coverings, i.e. inner plasma membrane, middle glycoprotein, zona pellucida and outer cellular corona radiata with radially elongated scattered cells held in mucopolysaccharide (hyaluronic acid).

✒ Menstrual Cycle: -

It is a rhythmic change in the reproductive organs of the female primates (monkey, apes and humans). 

(i) The first menstruation begins at puberty and is called menarche. 

(ii) Average interval of menstruation in human female is about 28-29 days. 

(iii) The cyclic events starting from one menstruation till the next one constitutes one menstrual cycle. 

(iv) The four phases of menstrual cycle are: -

✅Menstrual Phase: -

(a) Cycle starts with this phase and the menstrual flow occurs for 3-5 days.

 (b) It occurs due to breakdown of endometrial with lining of the uterus and blood vessels which along unfertilized ovum comes out through the vagina. 

(c) Menstruation occurs only if fertilization does not take place.

(d) Lack of menstruation generally indicates pregnancy, but may also be due to stress, poor health, diseases, etc. 

✅Follicular or Proliferative Phase: - 

(a) Menstrual phase is followed by the follicular phase.

(b) The primary follicle in the ovary grows to become a fully mature Graafian follicle and simultaneously the endometrium of uterus regenerates through proliferation.

(c) Pituitary and ovarian hormones induce the changes in ovary and uterus. 

(d) LH and FSH levels increase gradually during this phase and stimulates follicular development. 

(e) The growing follicles secrete oestrogens. 

(f) Both LH and FSH attain highest level during mid-cycle (about 14th day)

✅Ovulatory Phase: -

(a) Rapid secretion of LH leading 1o its maximum level during the mid-cycle is called LH surge. 

(b) The LH surge induces rupture of Graafian follicle, releasing the ovum and this process is called ovulation.

✅Luteal Phase/Secretory Phase: -

(a) Ovulatory phase is followed by the luteal phase. 

(b) The remaining parts of the ruptured Graafian follicle change into corpus luteum. 

(c) Corpus luteum secretes large amount of progesterone, which is required for the maintenance of endometrium. 

(d) The thickened endometrium is necessary for the implantation of fertilized ovum and maintenance of pregnancy. 

(e) During pregnancy, all the events of menstrual cycle stop, and menstruation does not occur. 

(f) In case of no fertilization, the corpus luteum degenerates and now known as corpus albicans, which does not secrete progesterone. This causes rupture of endometrium leading to menstruation - initiation of a new cycle. 

(v) In human females, menstrual cycle stops around the age of 50 years and this phase is called as menopause. 

(vi) Menstrual cycle is absent temporarily during pregnancy and lactation periods and permanently after menopause. 

(vii) Menstruation is also called 'Weeping of uterus for the lost ovum' or "Funeral of unfertilized eggs'.

Human Reproductive system, Male Reproductive System, Female Reproductive System, Mammary glands,

Human Reproductive system

✅ Male Reproductive System: -

It includes a pair of testes, accessory ducts, glands and the external genitalia. 

(i) Testes are located outside the abdominal cavity within a pouch called scrotum which maintains the low temperature of the testes (2-2.5°C lower than the normal body temperature) required for spermatogenesis.

(a) Each testis is oval shaped with a length of 4-5 cm, width of 2-3 cm and covered by a dense covering called tunica albuginea.

(b) Internally it is divided into about 250 Compartments known as testicular lobules. 

(c) Each lobule contains 1-3 highly coiled structural and functional units of testis called seminiferous tubules in which sperms are produced. 

(d) Seminiferous tubule is lined on its inside by two types of cells called male germ cells or spermatogonia and Sertoli cells 

(e) Male germ cells undergo meiotic divisions leading to the formation of spermatozoa. 

(f) Sertoli cells provide nutrition to the germ cells and hence called nurse cells. 

(g) Interstitial spaces are present in between the seminiferous tubules which contain small blood vessels and Interstitial cells or Leydig cells. 

(h) Leydig cells synthesis and secrete the testicular hormones called androgens mainly testosterone.

(ii) Male accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. 

(a) The intratesticular duct system starts with tubuli recti, which are short, straight end segments of the seminiferous tubules. These tubules connect the seminiferous tubules to the highly anastomosing, cuboidal epithelium-lined channels called rete testis.

(b) From rete testis, 10-25 fine tubules arise called vasa efferentia that leave the testis and open into the epididymis. 

(c) Epididymis leads to vas deferens that ascends to the abdomen and loops over the urinary bladder. It receives a duct from the seminal vesicle to form ejaculatory duct that runs through the prostate and opens into urethra. 

(d) Urethra receives the ducts of prostate gland and the bulbourethral gland (Cowper's glands) a little ahead and runs through the penis to its external opening called urethral meatus.

(iii) The accessory glands of male reproductive system include 

(a) A pair of seminal vesicles, a prostate gland and a pair of bulbourethral glands (Cowper's glands). 

(b) The secretion of all these glands is called seminal plasma. 

(c) Seminal vesicles secrete alkaline seminal fluid that contains fructose, citrate, prostaglandins, etc. 

(d) Prostate gland secretes slightly acidic (pH-6.5) milky fluid containing calcium proteolytic enzymes, etc. This fluid nourishes and activates spermatozoa to Swim, i.e., it provides sperm motility. 

(e) Secretion of bulbourethral glands is alkaline, and it helps in the lubrication of the urogenital tract. It also neutralizes any acid of urine present in urethra. 

(f) Seminal plasma along with sperms is called semen. 

(iv) External genitalia are the penis. It is made up of special erectile tissue that helps in erection of the penis. The enlarged tip of the penis is called glans penis. It is covered by a loose fold of skin called foreskin or prepuce.

Female Reproductive System: -

It consists of a pair of ovaries, secondary sex organs, external genitalia and mammary glands. 

(i) Ovaries are primary female sex organs. which produce female gametes called ova and secrete the female sex hormones. 

(a) These are located one on each side of the lower abdomen. 

(b) These are almond-shaped, 2-4 cm in length and 1.5 cm in width. 

(c) Each ovary is connected to the pelvic wall and uterus by ligaments. 

(d) Each ovary is covered by a thin epithelium which encloses the ovarian stroma.

(e) Ovarian stroma is divided into two regions, i.e., peripheral cortex and inner medulla. 

(ii) Other structures associated with female reproductive system are accessory ducts or oviducts or Fallopian tubes, uterus and vagina. 

(iii) Each Fallopian tube is about 10-12 cm long and extends from the periphery of each Ovary to the uterus. 

(a) The part of oviduct closer to the ovary is funnel-shaped and is known as infundibulum. 

(b) The edges of infundibulum possess finger-like projections called fimbriae, which help in the collection of ovum after ovulation. 

(c) Infundibulum leads to a wider part of the oviduct called ampulla.

 (d) Isthmus is the last part of the oviduct, which has a narrow lumen, and it joins the uterus 

 Figure 3.2 Female reproductive system (a) Lateral view (b) S

(iv) Uterus or womb is a pear-shaped muscular organ. It is about 75 cm long and 5 cm wide. It is attached to the pelvic wall and supported by ligaments. 

(a) Wall of the uterus has three layers of tissue. 

(b) Perimetrium is the outermost thin membranous layer, myometrium is the middle thick layer of smooth muscles and endometrium is the innermost glandular layer which lines the uterine cavity. 

(c) Uterus opens into the vagina through a narrow cervix, its cavity is called cervical canal, which along with vagina forms birth canal. 

(d) Endometrium layer undergoes cyclic changes during menstrual cycle. 

(e) Smooth muscles in myometrium contract during parturition to deliver the baby. 

(v) Vagina is a muscular tube-like structure that opens to the outside. It receives spermatozoa during insemination and serves as birth canal. 

(vi) Female external genitalia

✒Include mons pubis, labia majora, labia minora, clitoris and hymen. 

(a) Mons pubis is a cushion of fatty tissue covered by skin and pubic hair. 

(b) Labia majora are fleshy folds of tissue which extend down from the mons pubis and surround the vaginal opening. 

(c) Labia minora are paired folds of tissue under the labia majora.

(d) Hymen is a membrane that covers the opening of vagina partially. It gets ruptured during vigorous physical activities or during the first coitus. 

(e) Clitoris is a tiny finger-like structure, which lies at the upper junction of the two labia minora above the urethral opening. It is homologous to male penis. 

(vii) Mammary glands (breasts) are paired structures that contain glandular tissue and variable amount of fat. 

(a) Glandular tissue of each mammary gland is divided into 15-20 mammary lobes containing the cluster of cells called alveoli. 

(b) The cells of alveoli secrete milk, which is stored in the cavities (lumen) of alveoli. 

(c) Alveoli open into mammary tubules. The tubules of each lobe join to form a mammary duct.

(d) Several mammary ducts join to form a wider mammary ampulla, which is connected to lactiferous duct through which milk is sucked out.

Sexual Reproduction, sexual reproduction in flowering plants, events of sexual reproduction, gamete transfer, fertilization,

   Sexual Reproduction   

In sexual reproduction, two parents of opposite sex participate along with fusion of male and female gametes. All organisms have to reach a certain stage of growth and maturity in their life cycle before they reproduce sexually. Life cycle of an organism is divided into the following three phases: - 

(i) Juvenile or Vegetative phase - pre-reproductive period 

(ii) Reproductive phase - Reproductive period 

(iii) Senescent phase - End of reproductive period leading to ageing.

Sexuality in Organisms: -

On the basis of gametes, sexuality in organisms can be classified as follows Sexuality in Plants: -

(i) Homothallic or Monoecious plants Both male and female flowers are present on same plant body (bisexual condition) and the gametes belong to the same parent, e.g. in several fungi like Mucor and plants like maize, cucurbits and coconuts. 

(ii) Heterothallic or Dioecious plants Male and female flowers are present on separate plant body- (unisexual condition) and the gametes belong to different parents, e.g. papaya and date palm. In flowering plants, the unisexual male flower is staminate, while female is pistillate.

 Sexuality in Animals: -

(i) Bisexual animals have both male and female organs in single individual, e.g. earthworm, sponge, leech, tapeworm, etc. These are also called as hermaphrodites. 

(ii) Unisexual animals have male and female organs in different individuals, e.g. cockroach human, dog, etc.

Features of Sexual Reproduction: -

(i) Reproduction is a seasonal phenomenon in some organisms. Based on the season of reproduction in majority of plants, following categories can be made 

(a) Monocarpic plants Flowering occurs once in their life cycle after which they bear fruits and die, e.g. annual plants like rice, wheat, biennial plants like radish, henbane, etc. Bamboo species flower only once in their lifetime generally after 100 years. These produce large number of fruits and ultimately die. Similarly, Strobilanthes kunthiana (neelakurinji) flowers (blue in colour) bloom once in every 12 years.

(b) Polycarpic plants Flowering occurs every year in a particular season after reaching maturity, e.g. perennial plants like mango, apple, orange, etc. Few perennial plants flower throughout the year, e.g. China rose. 

(ii) Similarly, in animals, on the basis of time of breeding, the categories are: -

(a) Seasonal breeders breed at a particular time of the year, e.g. frogs, lizards, birds, etc. 

(b) Continuous breeders reproduce throughout their lifespan of sexual maturity, e.g. cattle, poultry, rabbit, etc. 

(iii) During reproductive phase in placental mammals, many cyclic changes occur in the reproductive system of females, i.e. 

(a) In non-primate mammals such as cow, sheep, rat, deer, dog, tiger, etc., the cyclic changes occurring during reproduction are termed oestrus cycle

(b) In primate mammals, such as monkeys, apes and humans, the changes cyclic occurring during reproduction are termed as menstrual cycle.

Events in Sexual Reproduction 

The events of sexual reproduction occur in the following three stages: - 

1) Pre-fertilisation the two main pre-fertilisation events are as follows Gametogenesis It is the formation of male and female gametes. Types of gametes are: - 

(i) Homogametes or Isogametes Gametes, which are not differentiated as male and female gametes, e.g. algae such as Ulothrix. The fusion of these gametes is called isogamy.

(ii) Heterogametes, which are morphologically distinct, e.g. gametes in human, i.e. sperm (male) and ovum (female). The fusion of these gametes is called anisogamy.

Cell Division during Gamete Formation: -

(i) Gametes are always haploid, but they divide either by mitotic or meiotic division. The organisms belonging to Monera, Fungi, algae and Bryophyta. have haploid plant body. These organisms produce gametes by mitotic division.

(ii) In pteridophytes, gymnosperms, angiosperms and most of the animals including humans, the parental body is diploid. In these organisms, specialised cells called meiocytes or gamete mother cells undergo meiosis that results in the formation of haploid gametes.

Gamete Transfer: -

It occurs in various ways in different organisms.: - 

(i) In most organisms, male gamete is motile and female gamete is non-motile. 

(ii) Both gametes are motile in few fungi and algae.

(iii) In algae, bryophytes and pteridophytes, gamete transfer takes place through water by producing many male gametes to ensure fertilisation because during gamete transfer, large number of male gametes are lost. In bryophytes and pteridophytes, male gametes are known as antherozoid. 

(iv) In self-fertilising or bisexual plants, e.g peas, gamete transfer is easy as the anthers and stigma are closely located. In Cross-fertilising plants, gamete transfer occurs by pollination. It is the process of transfer of pollen grains from anther to stigma, e.g. dioecious plants. 

2) Fertilization (Syngamy): -

It is the process of fusion of male and female gametes, which leads to the formation of a diploid cell, known as zygote. Depending upon, where does the syngamy occur, fertilization may be of two types 

(i) External fertilisation It is the fusion of gametes that takes place outside the body of an organism in external medium such as water, e.g. in bony fishes, frogs, etc. A large number of gametes are released in the surrounding medium by such animals. 

(ii) Internal fertilisation It is the fusion of gametes that takes place inside the body e.g. in fungi, higher animals Such as birds, mammals and majority of plants. The number of ova produced is less, but a large number of male gametes are formed, as many of them fail to reach the ova. In some lizards, birds, honeybees and rotifers, female gamete undergoes development to form offspring without fertilisation. This is called parthenogenesis. In honeybee queen, 32 chromosomes are present, During the development of eggs within a queen, a diploid cell with 32 chromosomes divides to generate haploid cells called gamete with 16 chromosomes. Now this haploid egg with 16 chromosomes forms new offspring (known as drone) without fertilisation.

3). Post-fertilisation Events: -

After the fusion of male and female gametes, following processes occur: - 

(i) Formation of zygote is the beginning of new life. It is always diploid and ensures the continuity of race from generation to generation. Organism such as fungi, develops a thick wall around it that is resistant to external damaging factors. Zygote divides by meiosis to form haploid Spores that grow into haploid individuals in case of organisms which lead haplontic life cycle, e.g. Volvox, Spirogyra, etc. In organisms with diplontic life cycle, zygote undergoes mitotic division and develops into an embryo, e.g. all flowering plants. 

(ii) Embryogenesis is the process of development of embryo from zygote. The events which occur in animals during embryogenesis are 

(a) Mitosis (Cell division or Cleavage) occurs leading to the growth of embryo. 

(b) Cells of embryo undergo differentiation and attain specific shape, size and function.

(c) Cell differentiation leads to the production of different tissues, organs and organ systems. 

(d) Depending on the development of embryo the animals can be, 

✅Oviparous animals, e.g. reptiles and birds. Here, embryo develops outside the body of female (eggs). In these animals, the fertilised eggs are covered by hard calcareous shell. 

✅Viviparous animals, e.g. majority of mammals including humans. Here, embryo develops inside the body of female. 

The post-fertilisation events that occur in flowering plants are: -

✅ Sepals, petals and stamens wither and shed off. 

✅Pistil remains attached to the plant. 

✅Zygote develops into embryo and the ovules develop into seed. 

✅Ovary develops into the fruit. 

✅Pericarp is produced as the wall of ovary. Seeds disperse by different agents and germinate into new plants after getting suitable conditions.

Organisms such as aphids, slime Moulds, sea-anemones and many plants switch from asexual to sexual mode of reproduction, when environmental conditions are unfavorable. Sexual reproduction leads to variation in offspring, thus providing a mechanism for selective adaptations to occur.

Chemical reaction, type of reaction, chemical reaction in chemistry, 10 most important chemical reaction in chemistry,

  Chemical Reactions  

In chemistry there are many types of chemical reactions some reactions are in generally known as naming reactions. Some reactions are: - Wurtz reactions, Grignard reactions, Fitting reactions, Wurtz Fitting reactions, Williamson's synthesis, Kolbe's Electrolysis reactions, Friedel Craft Acylation reactions, Friedel Craft Alkylation reactions, Diazotization Reactions, Hoffmann's Bromide reactions, Carbylamine reactions, Riemer - Tiemann Reaction,  Finkelstein reaction, Clemmensen reduction, Esterification Reaction, Cannizzaro's Reactions, Elb's Reactions, Ullmann reactions, Étard's reactions, Sandmeyer reactions, Aldol Condensation reaction, Markownikoff's Rule, Antimarkownikoff's rule, Tollen's Reagent, Fehling solution, 

✅Wurtz Reactions- The reactions in which higher alkanes are prepared by heating of alkyl halides (RX) with sodium (Na) in the presence of dry ether is called Wurtz reactions.

✅Grignard Reactions: - The reactions in which alkyl maghalide(RMgX) is prepared by heating or alkyl halide (R-X) with Mg in the presence of dry ether is called Grignard Reactions.

✅Fitting Reactions: -The reactions in which di aryl is prepared by heating of two molecules of aryl halides with sodium in the presence or dry ether is called fitting reactions.

✅Wurtz Fitting Reactions: - The reactions in which allyl benzene is prepared by heating of alkyl halide and aryl halides with Na in the presence of dry ether is called Wurtz fitting reactions.

✅Williamson's Synthesis: -The reactions in which ethers (-0-) are prepared by heating of alkyl halides with sodium alkoxide (Na-0-R) or, sodium phenoxide is called Williamson's synthesis.

✅Kolbe's Electrolysis Reactions: - The electrolysis of Na/K salts of carboxylic acid in aqueous solution to give alkane, alkene and alkyne is called Kolbe' s electrolysis reactions.

✅Friedel Craft Alkylation: - he reactions in which alkyl benzene is prepared by heating of alkyl halides with benzene in the presence of anhydrous AlCl3 is called Friedel craft alkylation.

 

✅Friedel craft Acylation:  - The reactions in which aromatic ketones (R-CO-Ar) are prepared by heating of acid chloride(R-CoCl) or, anhydride with benzene in the presence of anhydrous AlCl3 is called Friedel Craft Acylation.

✅Diazotization Reactions: - The reactions in which benzene diazonium chloride is prepared by heating of aniline, dilute HCl/ H2So4 and cold HNO2 at 0'c-5'c is called diazotization reactions.

✅Hoffmann's Bromide reactions: - The reactions in which P- amine is prepared by heating of amides (R-CoNH2), Br2 and KOH/NaOH solution is called Hoffmann's bromide reactions

✅Carbylamine Reactions: -The reactions in which alkyl isocyanide is prepared by heating of P- amine (R-NH2), chloroform and KOH solution is called carbylamine reactions.

✅Riemer- Tiemann Reactions: - The reactions in which hydroxy benzaldehyde ( salicyldehyde) is prepared by heating of phenol: CHCI3 and KOH solution at 340k is called Riemer Tiemann reaction.

✅Finkelstein Reactions: - The reactions in which chloroalkane or bromoalkene is treated with Nal dissolved in acetone is called Finkelstein reactions. 

✅Clemmensen Reduction: -The reactions in which aldehyde or ketone is reduced wit ZnHa/conc. HCI to form alkanes is called Clemmensen reduction.

✅ Esterification Reactions: - The reactions in which esters is prepared by heating of carboxylic acid with an alcohol in the presence of conc. H2s04 is called esterification reactions.

✅Cannizzaro's Reactions: - The reactions in which the aldehyde is treated with conc. NaOH to form sodium salt and an alcohol is called Cannizzaro's reactions. 

✅Elb's Reactions: - The reaction in which phenol is oxidised with K2S2O8 to form O/P dihydroxy benzene is called Elb's reactions.

✅Ullmann Reactions: - The reactions in which two molecules of iodo benzene is heated with Cu to form biphenyl is called Ullmann reactions. 

✅Étard's Reactions: - The reactions in which Toluene (methyl benzene) is oxidised with chromyl chloride in the presence of CCI4 or CS2 to form benzaldehyde is called Étard's reactions.

✅Sandmeyer Reactions: - The conversion of benzene diazonium chloride into chlorobenzene, bromobenzene or cyanobenzene with CuCl/HCI, CuBr/HBr, CuCn/KCn is called Sandmeyer reactions.

✅Aldol Condensation Reactions: - The reactions in which aldehyde or ketones is heated with dil. NaOH to form B-hydroxy aldehyde or B- hydroxy Ketones is called aldol condensation reactions.

✅ Markownikoffs Rule: - According to this rule, the negative part or a reagent (HX) will be attached to an alkene or alkyne with less numbers or hydrogen atoms is called Markownioff's rule.

✅Antimarkownikoff's rule: - According to this rule, the negative part of a reagent (HX) will be attached to an alkene or alkyne with higher number or hydrogen atom in the presence of peroxide is called Antimarkownikoff's rule. 

✅Tollen's Reagent: - The mixture of NH40H and AgNo3 is called tollens reagent.

✅Fehling Solution: - The mixture of Cuso4 and NaOH is called Fehling solutions.