Category: 12th Zoology

Ovulation and fate of the ovum – Menstrual cycle

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Post date October 16, 2018
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Ovulation and fate of the ovum – Menstrual cycle

The shedding of the ovum from the ovary is called ovulation. The ovarian
follicle enlarges and reaches the surface of the ovary. The stroma and the theca
of the Graffian follicle ruptures and the ovum is shed from the ovary. As it reaches
the fallopian tube it may get fertilized. The fertilized egg reaches the uterus and
gets implanted on its wall. If the ovum is not fertilized in the fallopian tube it dies
in 12- 24 hours.

Corpus luteum

The corpus luteum is an important structure needed at the time of
pregnancy. It is derived from the empty graafian follicle after ovulation. The
corpus luteum secretes a hormone called progesterone. It is a steroid hormone,
secreted in significant amounts by the corpus luteum and placenta.

Menstrual cycle

The functioning of the reproductive system in human adult female is
characterized by the menstrual cycle. While the changes concerned within ovulation and the formation of the corpus luteum, are going on in the ovary, the uterine endometrium shows striking cyclical changes.

The rhythmical series of changes in the sex organs occur for about 28 days through out the reproductive life of women from puberty to menopause (except during times of pregnancy). It is called the menstrual cycle.

The most prominent feature of this cycle is a monthly flow of blood from
the genital canal. This is called menstruation or menses. A menstrual cycle begins with the onset of menstrual bleeding and ends just before the next menstruation.

The menstrual cycle is usually divided into the following phases on
the basis of changes taking place in the uterine endometrium.
The follicular phase or Proliferative phase ( 5th day – 14th day)

The follicular phase is initiated by the release of follicle stimulating
hormone (FSH) from the anterior pituitary gland. During this phase, a
primary follicle begins to enlarge. While it is growing, the follicles secrete
oestrogen and smaller quantities of progesterone into the blood. Under the
effects of oestrogen from the developing follicle, the endometrium starts
regenerating from the basal portion. Deeper parts of the glands start proliferating.

By day 14, graffian follicle has matured and pushed up against
the ovary surface. The secretion of FSH ceases at the end of follicular phase.
The Luteal phase or Premenstrual phase (15th day – 28th day)

The luteal phase begins at day 14. Under the influence of Leutenizing
hormone (LH) released by the anterior pituitary, rupture of graffian follicle
and release of ovum (ovulation) occurs. After ovulation, the empty follicle is
transformed into a transitory endocrine gland called corpus luteum. The
corpus luteum slowly increases in size and releases a large quantity of
progestrone and smaller amount of oestrogen into the blood.

The progesterone acts on endometrium of the uterus, preparing it to receive the
fertilized ovum. To maintain pregnancy and to prevent the contraction of
uterus, the progesterone hormone is highly essential. If there is no fertilisation,
the corpus luteum degenerates and is reabsorbed by the ovary at the end of
luteal phase.

The menstrual phase (1st – 5th day)

The decline in progesterone and oestrogen initiates shedding of the
endometrium and severe bleeding in a process called mensus or
menstruation. During this phase, all the extra layers are sloughed off along
with unfertilized egg. At the termination of menstruation, the corpus luteum is
converted into a scar tissue called corpus albicans.

Functioning of female reproductive system

Post author By Mr. Padeepz
Post date October 15, 2018
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Functioning of female reproductive system

The central role of the female reproductive system is carried out by the ovaries. They produce sex cells called ova or eggs containing genetic material.

By a process of fertilization an egg derives the potentiality to develop into a foetus. The ovaries also secrete female sex hormones that control sexual development and the menstrual cycle

Endocrine function of Ovary (Female Sex Hormones)

The ovaries produce the female sex hormones oestrogen and
progesterone. The secretion of these hormones are controlled by follicle – stimulating hormone and lutenizing hormone which are produced by pituitary gland.Female sex hormones control sexual development at puberty, the menstrual cycle and fertility.

Oestrogens (Functioning of female reproductive system)

These are steroidal hormones secreted by the theca interna of the ovum, cells of graffian follicle, corpus luteum and placenta. Oestrogen hormone controls the development of accessory sex organ and secondary sexual characters. It regulates menstrual cycle. Oestrogen promotes growth of ovarian follicles. Further it causes the growth of the breasts and formation of melanin pigments.

Progesterone is the principal hormone secreted by the corpus luteum. It prepares the uterus for implantation of the fertilized ovum.It helps in the formation of placenta and for maintaining pregnancy.

Further during preguancy it inhibits contraction of uterus. It also suppresses ovulation and menstruation in pregnancy.

Structure of a mature ovum (Functioning of female reproductive system)

Human ovum is small and contains no yolk (Alecithal egg) It is more than 100mm in diameter At the time of ovulation, the ovum is surrounded by a striated membrane called zona radiata and later it is replaced by an unstriated membrane Zona pellucida (Primary egg membrane). The growing oocytes are surrounded by follicle cells.

Some of the follicular cells of the ovary are found outside the zona pellucida and are termed as Corona radiata (Secondary egg membrane) which is peeled off when the oocyte passes down the oviduct. The follicles and the developing oocyte
together constitute Graafian follicle. The whole surface of the graafian follicle is supported by theca interna and theca externa.

Functioning of male reproductive system

Post author By Mr. Padeepz
Post date October 15, 2018
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Reproduction (Functioning of male reproductive system)

All living organism maintain their populations by reproduction. Most
simple organisms such as bacteria reproduce asexually by cell division
resulting in offspring’s that are genetically identical.

In human beings, reproduction is sexual, involving the fusion of two
reproductive cells, namely a sperm (male gamete) and an egg (female gamete).
If a sperm succeeds in fertilizing an egg, DNA (genetic material) from
each parent combines to create a unique individual. Sexual reproduction results
in an infinite variety of offsprings.

Functioning of male reproductive system

The central role of the male reproductive system is carried out by the
testes, which produce sex cells called spermatozoa or sperms containing
genetic material. The testes produce sperms continuously from puberty onward.

Men remain fertile for a much longer period than women. In addition, the testes
manufactures male sex hormones or androgens which influence sperm
production, fertility and sex drive. Male sex hormones also promote the
secondary sexual characters.

Gametogenic function of testes (male reproductive system)

Factors controlling spermatogenesis: FSH of pituitary gland
stimulates and controls spermatogenesis. It acts on sertoli cells to facilitate
last stages of maturation of spermatids. It further stimulates the production of
androgens such as testosterone.

The LH of the pituitary acts on the Leydig’s cells of the testes that
releases testosterone. The temperature of testes should be maintained at
32oC for an effective production of spermatozoa.

Spermatozoa (male reproductive system)

Each mature spermatozoan is a motile cell . It has an oval flat head
having an acrosome and a large nucleus containing chromosomal material. The
head is followed by a short neck, a body (middle piece) and a long tail.

The middle piece contains spiral mitochondrial sheaths which are the site of energy production. The tail has a main piece and an end piece. The energy for movement is provided by ATP molecule.

Puberty (male reproductive system)

Puberty is a process in sexual development. Once puberty is reached
sperms are manufactured continuously in the two testes at a rate of about 125
million each day.

Puberty occurs between age 12-15 Hormones secreted by the pituitary cause levels of the male sex hormone testosterone to increase, stimulating changes such as general growth, and the development of secondary sexual characters.

Transport of spermatozoa. For reproduction to take place, the sperm must be
transported to the female reproductive system. The mature spermatozoa that are
formed leave each testis through an epididymis, a long coiled tube that lies above and behind each testis.

The sperms are stored in the epididymis and periodically pushed into the vasdeferens the tube that connects an epididymis to an ejaculatory duct.

During sexual activity each vas deferens, contracts and pushes the sperm toward urethra, the tube that connects the bladder to the outside of the body. The sperms are carried in a fluid consisting of secretions from various glands forming a thick seminal fluid or semen.

Semen is a milky mucoid fluid which contains sperms (50 million in single
ejaculate) plus seminal plasma made up of secretions of the seminal vesicles,
prostate, Cowper’s gland and bulbo – urethral glands. Semen provides nutrient
that help to keep the sperm healthy and also serves as a medium for the
spermatozoa to swim.

During arousal, the penis gets enlarged and becomes firm. Muscular
contraction at the have of the penis then forces the sperm through the male
urethra into the vagina during male orgasm.

Hormonal control (male reproductive system)

Male reproductive function is controlled by several hormones.

1. The hypothalamus of the brain controls the release of FSH and LH through
its releasing factors.

2. FSH and LH stimulate the gonads. Hence the gonads produce sperms
and secrete the hormone, testosterone.

3. Testosterone controls further male reproductive functions. It also helps to
develop and maintain secondary sexual characters, such as enlargement of
larynx, deepening of voice, growth of hair and other adolescent changes.
Regulation of testicular function

The hypothalamus, anterior pituitary and testes are interrelated in
testicular functions. FSH from the pituitary stimulates spermatogenesis in the
presence of testosterone. High concentration of testosterone is maintained due
to the presence of androgen binding protein which is secreted by the sertoli cells.
These cells also secrete another hormone called inhibitin which inhibits the action
of testosterone.

Testosterone secretion by Leydig cells is stimulated by LH. The
testosterone has its action on different target cells. It diffuses into the seminiferous tubules and stimulates spermatogenesis and suppresses secretion of LH by acting on hypothalamus and anterior pituitary.

Diabetes mellitus

Diabetes mellitus is the metabolic disorder of carbohydrate
metabolism caused by insufficient or nil production of the hormone insulin
by the pancreas. Insulin is responsible for the absorption of glucose into
cells for their energy needs and into the liver and fat cells for storage as
glycogen reserve. Insulin deficiency may be due to (1) pancreatic disorders
(2) defects in the synthesis of insulin from Beta cells of Langerhans
(in pancreas) (3) destruction of Beta cells and (4) genetic defects etc.

Symptoms of Diabetes mellitus

(1) The blood sugar level is more than 120mg. in diabetic patients.

(2) Untreated diabetes exhibits the following symptoms.
(a) Polyurea – excretion of increased quantity of urine.
(b) Polydipsia – excessive thirst leading to increased consumption of water.
(c) Polyphagia – excessive appetite leads to increased in take of food. In
spite of over eating, diabetic patient looses weight.

(3) Weakness and body pain are the common symptoms.

(4) The body’s inability to store or use glucose causes weight loss, insatiable
hunger and fatigue.

(5) Diabetes mellitus also results in abnormal (fat) metabolism.

(6) Accelerated degeneration of small blood vessels.

Type’s of diabetes mellitus

(1) Insulin –dependent type.
(2) Non-insulin dependent.

Insulin-dependent type: This type develops due to heavy viral infection which
reduces the production of insulin.

Non-insulin dependent: This is due to inadequate amount of insulin
production. Obesity (over weight) is the major reason. This type usually of
gradual onset and develops mainly in people over 40. Recently insulin
resistant diabetes is commonly noticed and reported in younger persons too.

Causes for Diabetes

(1) Diabetes tends to run in families so it occurs in people who inherit the
genes responsible for the insulin dependent form.
(2) Viral infection that damages the pancreas causing the deficiencyof insulin.
(3) Obesity is the major cause leading to development of non insulin dependent
diabetes.
(4) Severe illness such as pancreatitis and thyrotoxicosis causes diabetes.
(5) Intake of drugs like corticosteroid drugs and diuretic drugs.

The preventive measures comprise

(1) Maintenance of normal body weight through adoption of healthy
nutritional habits and physical exercise.
(2) Correction of over nutrition and obesity may reduce the risk of diabetes
and its complications.
(3) Alcohol and smoking should be avoided.
(4) Control of high blood pressure, elevated cholesterol and high triglyceride
levels.
(5) Susceptible persons can prevent diabetes by avoiding the risk factors.

When diabetes is detected, it must be adequately treated.In order to
maintain blood glucose levels within the normal limits one should maintain
ideal body weight. It is achieved by balanced diet, physical exercise, frequent
checking of blood sugar, blood pressure. Maintenance of body weight and
visual acuity are some prognostic tips.

Kidney stone – Kidney transplantation

Post author By Mr. Padeepz
Post date October 14, 2018
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Kidney stone and Kidney transplantation

Kidney stone (Calculus)

Stone formation in the kidneys, Ureters or Bladder, is caused by the
precipitation from the solution of the substances in urine. Kidney and Ureter
stones are more common than Bladder stones.

The incidence of stone formation is highest in summer months as the urine is more concentrated due the loss of fluid in the sweat.

The stones tend to be a recurrent problem. Chronic dehydration is the main cause for kidney stones. Kidney stone consists mainly of calcium oxalate and/or phosphate.

Stone consists mainly of uric acid and may occur in people with GOUT.
Bladder stone usually develops as a result of a diet that is low in
phosphate and protein.

The most common symptom of a stone in the kidney or ureter is renal cholic (a severe pain) and the symptom for the bladder stones manifest with difficulty in passing urine.

Stones in the bladder and lower ureter can be crushed and removed by cystoscopy or by ureterorenoscopy. The first line of treatment is lithotripsy which disintegrates stones by focusing shock waves on them from outside the body.

Kidney transplantation

Kidney transplantation refers to an operation in which a diseased
kidney is replaced by a transplanted healthy kidney, either from a living
donor or from a person who has just died (cadaver). One healthy donor
kidney is sufficient to maintain the health of the recipient.

Factors in improving the results of transplant surgery are

(1) To prevent rejection, effective immune suppressant drug treatment is given.
(2) Tissue typing is necessary to help in matching recipient and donor tissue
for transplant surgery thus minimizing the risk of rejection of a donor organ
by the recipient’s immune system.
(3) After removal of organ from the donor it should be washed with an
oxygenated fluid and cooled. This reduces the risk of damage.

Renal Failure, Dialysis, Kidney Machines

Post author By Mr. Padeepz
Post date October 14, 2018
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Renal Failure

The reduction in the ability of the kidneys to filter waste products
from the blood and excrete them in the urine is called as renal failure. The
regulation of the water balance, salt balance and control of blood pressure
are impaired due to kidney failure. The kidney failure also leads to uraemia
(a built up of urea and waste products) and other chemical disturbances in
the blood and tissues. This leads to various disorders and symptoms.

Kidney failure can be acute (of sudden onset) or chronic
(developing more gradually). In acute Kidney failure kidney function returns
to normal once the causes have been discovered and treated. In chronic
kidney failure the kidney function does not revive since it is caused by poor
supply (flow) of blood, major illness, heart attack or pancreatitis. This
damages the kidney tissue and its function. Heart transplantation is suggested
for chronic type of failure.

Dialysis

Dialysis involves a technique used for removing waste products from
the blood and excess fluid from the body as a treatment for kidney failure.

Why it is done?

The kidneys filter approximately 1500 liters of blood daily. From this
volume of blood, the kidney reabsorbs important elements such as sodium,
potassium, calcium, amino acids, glucose and water. In people whose
kidney have been damaged this process may fail either suddenly (in acute
kidney failure) or gradually in chronic renal failure. Waste starts to
accumulate in the blood, with harmful, sometimes even life threatening
effects. In severe cases, the function must be taken over by artificial means
of dialysis. Dialysis is called artificial kidney.

Kidney Machines

A kidney machine is a mechanical device through which a patient’s
blood passes. The blood leaves the body usually from an artery in the
forearm and return to a nearby vein. Inside the machine the blood flows
over or between membranes containing dissolved fluid (Dialysing fluid) and
salt in concentrations normally found in blood. Solid constituents in the blood in excess of normal concentrations diffuse across the membrane into the
dialyzing fluid. In this way waste like urea which accumulate in the body are
extracted. Blood cells and protein remain in the blood. The process is called
haemodialysis.
Two kinds of dialysis are performed in clinical medicine. They are
haemodialysis and peritoneal dialysis.

Mechanism of urine formation

Post author By Mr. Padeepz
Post date October 8, 2018
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Mechanism of urine formation

Urine is continually formed by each nephron and the processes
involved in the formation of urine are

Glomerular ultra filtration, Tubular Reabsorption, Tubular Secretion

Glomerular ultra filtration (Mechanism of urine formation)

Ultrafiltration of blood takes place in the malpighian body which acts as a biological filter. A malpighian body comprises Bowmann’s capsule and glomeruli.

Dynamics of filtration (Mechanism of urine formation)

The kidneys normally receive an abundant blood supply of about
1200ml/min or about 20 to 25 percent of the cardiac output. It flows through
the capillaries of glomerulus where the blood pressure is comparatively high.
The high blood pressure brings about effective filtration. The hydrostatic
pressure (forward pressure 75mm/Hg.) of the blood in the afferent
glomerular capillaries and the cumulative effect of the opposition pressures
and renal intratubular pressure (10mm/Hg.) play an important role in
producing the glomerular filtrate. The hydrostatic pressure of the blood is
always greater than the opposing pressures existing in the plasma protein
and renal capillaries. Thus the available net filtering force (75-50mm/Hg. =
25mm/Hg.) is chiefly responsible for glomerular filtration. The fluid in the
capsule which is obtained by the process is termed glomerular filtrate. The
volume of the glomerular filtrate produced each minute is called glomerular
filtration rate (GFR). In man it is about 125ml/min. In 24 hours the total
volume of glomerular filtrate is 170 to 180 liters.

Tubular Reabsorption (Mechanism of urine formation)

This is the second step in the urine formation. The glomerular filtrate
contains many useful substances such as glucose, amino acids, mineral salts
and vitamins dissolved in large amount of water. Reabsorption takes place in
the uriniferous tubules. Reabsorption of useful substances is a differential or
selective process. Substances such as glucose, sodium and calcium, are called
“high threshold substance”. They are actively reabsorbed in
considerable quantities. Substances like urea and uric acid etc which are
called “low threshold substances” are reabsorbed in small quantities by a
simple diffusion process or passive reabsorption. Substances like creatinine
are not reabsorbed. They are completely eliminated.

Reabsorption in Proximal Convoluted Tubule (Mechanism of urine formation)

Proximal convoluted tubule is responsible for the reabsorption of
water, glucose, sodium phosphate and bicarbonates. The urine is found to

be isotonic in the proximal convoluted tubule. Isotonic condition of a
solution indicates no passage of water across the membrane separating two
such solutes.

Reabsorption in Henle’s loop

Urine becomes more and more hypertonic as it passes through the
descending limb of the loop of Henle’s. This is due to the fact that the thin
descending portions of the Henles loop are freely permeable to sodium. As
the urine slowly passes through the thick ascending limb of the loop of Henle,
it becomes less hypertonic since the sodium is actively transported from the
ascending limb to the descending limb through the interstitial tissue space.

Reabsorption in distal convoluted tubule

On entering the distal convoluted tubule, the urine becomes nearly
isotonic to the surrounding tissue fluid due to the active transport of sodium
and passive transport of water. Summary of Renal Filtration and
Reabsorption in 24 hours

Reabsorption in collection tubule

As urine (isotonic) passes into the collecting tubule it becomes once
more hypertonic by the osmotic reabsorption of water under the
influence of the hormone ADH. The release of ADH is controlled by the
osmoreceptors in the hypothalamus in response to changes in the osmotic
pressure of the plasma circulating through the collecting tubule. Thus the urine
formed contains 96% of water, 2% urea and 2% of the metabolic products.

Tubular Secretion

This is the final step in the formation of urine during which the walls
of tubule actively remove additional waste substances which are harmful to
the body from the blood that have escaped filtration.

Excretion Ureotelism Nephron

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Post date October 8, 2018
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Excretion Ureotelism Nephron

Excretion

As a result of continuous synthesis and breakdown of materials many
waste products are formed in cells. The process by which the cellular
nitrogenous wastes are eliminated is called excretion.

Three main nitrogenous wastes are ammonia, urea and uricacid. Various vertebrates excrete different form of nitrogenous wastes, according to the nature of their habitat and availability of water.

Ureotelism

Ureotelism is an adaptation for a semi-terrestrial habitat. Urea
requires only a small quantity of water to form urine and never involves much
water loss; Further, urea is much less toxic than ammonia and it can be
retained in blood for sometime before it is transported and eliminated through
the excretory organs. Though the concentration of urea in the blood is small,
it can be stored safely in the bladder in high concentration. Thus ureotelism is
conditioned by the shortage of water, characteristic of the terrestrial habitat.
Urea Biosynthesis (Ornithine Cycle)

Liver is the principal organ of urea biosynthesis. In the ornithine cycle,
ammonia, formed by deamination in cells and tissues, combines with carbon
dioxide to form carbamyl phosphate. This compound is subjected to a cyclic chemical reactions as provided in the figure. Three molecules of ATP are
spent to convert the toxic ammonia into a molecule of urea.

Nephron

Nephron is the structural and functional unit of the kidney. There are
about a million nephrons
In general, the kidney performs the following vital functions in the
body :
1. Excretion of waste products resulting from protein metabolism.
2. Regulation of acid-base balance by excretion of H+ ions (acidification)
and bicarbonate ions.
3. Regulation of salt-water balance by hormones secreted both intra-and
extra-renally.
4. Formation of renin and erythropoietin and thereby playing a role in the
regulation of blood pressure and erythropoises respectively.

Tongue – Mechanism of Stimulation

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Post date October 6, 2018
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Tongue – Mechanism of Stimulation

Tongue

In man the taste buds are found only in the mouth and are abundant in the
tongue. They are distributed over the dorsal and under surface of of the tongue,
on the laryngeal surface of the epiglottis, pharynx and on the cheek.

Each taste bud occupies the entire thickness of the epithelium. There is
an opening on its free surface known as the pore canal. Taste buds are
numerous at birth and their number decreases with age.

Taste sensation and disribution of taste cells

There are four primary or fundamental tastes. They are sweet, sour, salt
and bitter. Alkaline and metallic taste are also sometimes included.

Taste buds mediating the four primary taste are localized in certain
regions on the tongue. The taste bud sensitive to bitter taste are at the back of
the tongue. Those for sour tastes are on the lateral surface. Those mediating salt
at the anterior part of the dorsum near the tip. The taste bud sensitive to sweet
are near the tip.

The taste bud in the palate respond to sour and bitter taste but
have some sensitivity to sweet and salt. The pharynx and epiglottis are not
sensitive to all four tastes. It is found that both sweet and salt are insensitive to
taste in these regions.

Mechanism of Stimulation

Taste receptors are stimulated by substances in solution. The
dissolved substances act on the microvilli of the taste receptors which project
at the gustatory pore and sets up a generator potential to the receptor.

This inturn activates the afferent nerve ending at the base of the receptor, producing a propagated action potential in the nerve. The mechanism of
production of generator potential varies in different receptors of taste.

Dermatitis

It is inflammation of the skin, sometimes due to an allergy but in many
cases it occurs witout any known cause. Many types of dermatitis such as
eczema are known.

Contact dermatitis

In this type of dermatitis the rash is a reaction to some substances
that comes in contact with the skin. The reaction may result from a direct
toxic effect of the substances or it may be an allergic response.

Among the more common causes of the reaction are detergents, nickel (eg. in watch straps, bracelets, necklaces and fastening of underclothes), certain plants
(eg. Rag weed), certain cosmetics and some medications in the form of
creams, lotions or drops.

The type of rash varies according to the substance causing it but it is often itchy and may flake or lister. Distribution of the rash corresponds to the skin area that has been in contact with the causative substance.

Photo dermatitis

This type of dermatitis occurs in people whose skin is abnormally
sensitive to light. In the most common form of photo dermatitis a cluster of
spots or blisters develop on any part of the body exposed to sun.

Ovulation and fate of the ovum – Menstrual cycle

Menstrual cycle

The menstrual phase (1st – 5th day)

Related Topics in Zoology:

Functioning of female reproductive system

Endocrine function of Ovary (Female Sex Hormones)

Oestrogens (Functioning of female reproductive system)

Structure of a mature ovum (Functioning of female reproductive system)

Related Topics in Zoology:

Reproduction (Functioning of male reproductive system)

Functioning of male reproductive system

Gametogenic function of testes (male reproductive system)

Spermatozoa (male reproductive system)

Puberty (male reproductive system)

Hormonal control (male reproductive system)

Related Topics in Zoology:

Diabetes mellitus

Symptoms of Diabetes mellitus

Type’s of diabetes mellitus

Causes for Diabetes

Related Topics in Zoology:

Kidney stone and Kidney transplantation

Kidney stone (Calculus)

Kidney transplantation

Related Topics in Zoology:

Renal Failure

Dialysis

Kidney Machines

Related Topics in Zoology:

Mechanism of urine formation

Glomerular ultra filtration (Mechanism of urine formation)

Dynamics of filtration (Mechanism of urine formation)

Tubular Reabsorption (Mechanism of urine formation)

Reabsorption in Proximal Convoluted Tubule (Mechanism of urine formation)

Reabsorption in Henle’s loop

Reabsorption in distal convoluted tubule

Reabsorption in collection tubule

Tubular Secretion

Related Topics in Zoology:

Excretion Ureotelism Nephron

Excretion

Ureotelism

Nephron

Related Topics in Zoology:

Tongue – Mechanism of Stimulation

Tongue

Mechanism of Stimulation

Related Topics in Zoology:

Dermatitis

Contact dermatitis

Photo dermatitis

Related Topics in Zoology: