THE GENITO-URINARY SYSTEM
First there are the ovaries in the female anatomy. These are quite small and consist of masses of very small sacs called the ovarian follicles. Each follicle contains an egg.
The ovaries have two principle functions:
(1) To develop the ova and expel one at about 28 day intervals throughout the reproductive life.
(2) To produce hormones (oestrogen and progesterone) which influence secondary sex characteristics and control change in the uterus during the menstrual cycle.
The fallopian tubes: Function is transporting the ova from the ovaries to the uterus. The uterus is a muscular organ; it is positioned in the centre of the pelvis with the bladder in front and the rectum behind. It is usually divided into three parts; the fund's (the broad upper end) the body (the central part) and the cervix (the neck which projects into the vagina)
The vagina is a muscular canal, which connects the above organs to the external body at the point collectively known as the vulva, which includes the clitoris. This is a small sensitive organ containing erectile tissue corresponding to the male penis.
The male genital organs: These are fairly simple in comparison to the female genital organs. The principle organs are the testes, which are the essential male reproductive glands, the scrotum that is a pouch like organ containing the testes and the penis. This is suspended in front of the scrotum.
The Kidneys: These are positioned against the posterior abdominal wall at the normal waistline, with the right kidney slightly lower than the left. The kidneys consist of three principle parts; the cortex (outer layer which is bright reddish/brown) the medulla (middle portion which is inside red striated colour) and the pelvis (which is the hollow, inner portion from which the uterus open.)
The function of the kidneys is to separate certain waste products from the blood.
This function helps maintain the blood at a constant level of composition despite the variation in diet and in fluid intake. As blood circulates in the kidneys a large quantity of water, salts urea and glucose is filtered into the capsules of bowman and from there into convoluted tubulus. From here all the glucose most of the water and salts and some of the urea are returned to the blood vessels.
The remainder passes via the Calyces into the kidney pelvis as urine.
The kidneys process it each day although only about 1.5 litres of this leaves the body as urine. The urethras are two fine muscular tubes, which carry urine from the kidney pelvis to the bladder. This lies behind the Symphysis pubis and is an elastic muscular sac. The urethra is a narrow muscular tube passing from the bladder to the exterior of the body. In a female this is about 4 cm long but in a male about 20 cm long. In a male the urethra is the common passage for both urine and semen. Also in the male it passes through a gland known as the prostate gland. It surrounds the neck of the bladder and tends to enlarge after middle life.
Hormones: These are chemicals, which cause certain changes in particular parts of the body. They control things such as rate of growth, activity and sexual activity etc. The endocrine (ductless glands) secrete their hormones directly in to the blood stream and are circulated all over the body reaching their target organ via the bloodstream becoming relatively inactive compounds when they pass through the liver and are excreted through the kidneys. The endocrine system consists of a series of glands that secrete hormones, they are found through out the body and there is not really that much known about them. They include the pituitary, thyroid, parathyroid, thymus, supra-renal (adrenal) glands, part of the pancreas and parts of the ovaries and testes.
The Pituitary glands: This gland consists of two lobes, anterior and posterior.
The anterior lobe secretes many hormones including the Somatotrophic hormones, which are growth promoting and control the bones and muscles and in this way determines size. The anterior lobe also produces Gonadotrophic hormones for both male and female activity. Thyrotrophic hormones regulate the thyroid and Adrenocorticotrophic hormones regulate the adrenal cortex. It also produces metabolic hormones. The posterior lobe produces two hormones Oxytocin and Vasopressin. Oxytocin causes the uterine muscles to contract, it also causes the ducts of mammary glands to contract. Vasopressin is an anti diuretic hormone, which has a direct effect on the tubules of the kidney and increases the amount of fluid they absorb so that less urine is excreted. It also contracts the blood vessels in the heart and lungs and so raises blood pressure.
The Thyroid: The right and left lobes of this gland lie on either side of the trachea united by Ithmus. This secretion of this gland is Thyroxine and Tri-iodothyronine. Thyroxin controls the general metabolism, both hormones contain iodine but thyroxin is more active than thyroxin. This gland has a profound effect on both mental and physical activity.
The Parathyroid Gland: There are four of these glands two on either side lying behind the thyroid. They secrete Parathormone that raises the blood calcium as well as maintaining the balance of calcium and phosphorus in both the blood and bone structure.
The Thymus Gland: This gland lies behind the lower part of the neck. After puberty the thymus begins to atrophy so that in an adult only fibrous remnants remain. Its secretion is through to act as a brake on development of sex organs so that they thymus atrophies the sex organs develop. Recent research reveals it plays an important part in the body’s immune system by producing T lymphocytes (T=thymus derived)
The Supernal: Also known as the adrenal glands. There are two of these and they lie over each kidney. They are kidney shaped and divided into two parts, the cortex and the medulla. The cortex is the outer part of the gland and produces a number of hormones called Corticoid-steroids. Their function is to control sodium and potassium balance, stimulate the storage of glucose and affect or supplement the production of sex hormones. The medulla (inner layer) produces adrenalin, a powerful vasoconstrictor. Adrenalin raises the blood pressure and raises the blood sugar. The amount of adrenalin secreted is increased considerably by the end excitement fear etc.
The Gonads: (sex glands) these glands are different in men and women because they serve different purposes. The gonads in the female are the ovaries and in the male are the testes. Female sex hormones are oestrogen and progesterone. The Male hormone is testosterone although each produces a small quantity of the other.
The Pancreas: The endocrine part of the pancreas consists of clumps of cell called islets of langerhans, which secrete insulin. Insulin regulates sugar level in the blood and the conversion of sugar into heat and energy. Too little insulin results in a disease called diabetes mellitus.
General notes: The quantities involved in the secretion of various glands are minute.
So for example it is estimated the adrenal gland, which affect all of the organs of the body, only produce a maximum of 1 of hormone in a whole year