1.The small intestine has three structures to handle absorption; they are villi, microvilli, and the circular folds. The function of villi, microvilli, circular folds is to increase the surface area of absorption within the small intestine.
Microvilli are small projections of mucous membrane of small intestine walls. The microvilli give the small intestine walls as a brush border appearance. The structure of villi is similar to the microvilli except that villi are somewhat larger than the microvilli. Within the villi they are large number of capillaries. Villi are structures which act as valves, which allow solids, liquids and acids to pass through one structure to another.
Circular folds /valves of kerckring/plicae circularis are large valvular flaps projecting into the lumen of the bowel. They are made up of reduplication of the mucous membrane the two layers of the folds are bound together sub mucous tissue. They are permanent and are not obliterated when the intestine is distended. Circular folds slow the passages of food along the intestine and increase the surface area of absorption.
2.The structure and function of the filtration slit and membrane
There are three layers that make up the filtration membrane, two epithelia and the basement membrane that lies between them. The first epithelium is the endothelium that lines the glomerular capillaries this is fenestrated endothelium ie; there are pores that penetrate through the endothelial cells. The next layer the glomerular basement membrane, a shared basement membrane between the two epithelia. The outer epithelium consists of the podocytes ,cells with elaborate inter digitating processes known as the foot processes . Foot processes of neighboring podocytes join to form a dense network ie;which is an important component , the glomerular filtration barrier . The podocyte foot processes do not touch each other. The gaps between the foot processes are filled by a complex multiprotien structure called the slit diaphragm. Slit diaphragm are to allow the passage of excessive water and solutes from the blood into kidney ultra filtrate, while retaining larger plasma molecules..The excess water and solutes are filtered into the urinary space and subsequently pass into the system of renal tubule as kidney ulrtrafiltrate. The bigger molecules turn back at the glomerular filtration barrier, eventually re-enter the blood stream.
3.Structure and function and control of the internal and external urethral sphincters.
Urethral sphincter is a collective name for the muscles used to control the flow of urine from the urinary bladder. These muscles envelope the urethra so that , when they contract the urethra is sealed shut .The muscles originate at the pubic ramus with the insertion point at the median raphe . The function of the external sphincter is controlled by pudendel nerve and acts to constrict urethra
There are two urethral sphincters
Internal sphincter is located at the bladders inferior end an d the urethra’s proximal end at the junction of the urethra. With the urinary bladder. The int. sphincter is the continuation of the detrusor muscle and is made up of smooth muscles it is under involuntary or autonomic control .this is the primary muscle for prohibiting the release of urine.Ext.sphincter is located at the bladder distal end-females and inferior to the prostrate in males. It controls the flow of urine through the urethra. Unlike the int. sphincter muscle the external sphincter is made up of skeletal muscles. It is under voluntary control of the somatic nervous system .
4.The sperm are produced in the seminiferous tubules present in the testis . these tubules converge and collect in the form of a delta near the upper part of the testis called the retetestis the sperms then empty through a series of very small ducts called the efferent ducts out of the testis towards the epididymis .the tail of the epididymis then leads to the vas deference, a cord liuscular tube which is a part of the spermatic cord and which ends at the ejaculatory duct in the prostrate. In the prostrate the ejaculatory duct is joined by the seminal vesicle ducts and they all open into the urethra in the penis. Thus the sperms produced in the semineferous tubules follow the above path and finally come out of penis.
5.a) oestrogen hormone.
b) Internal iliac artery.
c.)Endometrium.