impulses cause the continence (i.e relaxation of tne detrusor and contraction of the sphincter). When the bladder is filled, the micturition reflex is

impulses cause the continence (i.e relaxation of tne detrusor and contraction of the sphincter). When the bladder is filled, the micturition reflex is initiated and now the maintenance reflex is overcome so that evacuation of bladder can occur applied physiology 1. Automatic bladder. From theoretical consideration it can be magined that when the spinal center is intact, the peripheral nerves supplying the bladder, as well as the bladder muscles, are healthy, but the connection between the higher (= cortical) and spinal centers are lost (or not developed), the bladder will be automatic, that is, whenever the filling of the bladder will reach a required point, the micturition reflex will be set up and evacuation will result, no matter whether it is convenient or inconvenient to pass urine Such a situation, i. e. automatic bladder, develops in a particular stage (phase) of transaction of spinal cord (for details, see chap. 8, sec. XD). In the Infants also, the higher control is not satisfactorily developed and so the evacuation of bladder is rather automatic. Retention Retention of urine in the bladder may be due to anatomical or functional reasons. Common anatomical causes are, (I) enlarged prostate (enlargement may be benign or cancerous) mechanically obstructng the urethral canal and (ji) stricture of the urethra (the stricture may be due to gonorrheal) infection). Functional causes are very commonly due to nervous system disorders. Thus, in the spinal shock (ch. 8, sec. XD) and in the initial phases of hemiplegia, the urine accumulates on and the bladder becomes distended and yet the bladder does not evacuate itself. Both in the spinal shock and earty stage of hemiplegia. spinal centers remain in a state of functionlessness for a variable period When they begin to regain funcbon, the function of the sphincter returns earlier than the detrusor, causing the retention. Effects of emotion it has been already stated that as the urine accumulates more and more, up to a certain stage, the detrusor relaxes so that pressure within the bladder does not rise and the desire for micturition does not develop. However, when a subject is excited or becomes anxious, the ability ofthe detrusor to relax is reduced and the desire for micturition develops even when the bladder contains only small quantity of urine. As a result frequency of urination can develop (e. g. in a panicky person). Effects of pregnancy Pregnancy causes a remarkable loss of tone of the detrusor muscle As a result, the pressure within the bladder remains low even when the volume of urine within it is quite high, and the desire to micturate does not occur. During urination, such bladder may not be completely emptied. The continued presence of residual urine may cause bacterial Infection which is rather common in pregnancy. Plainly, it is somewhat a3dn to the receptive relaxation of the stomach. 1. Functional anatomy: the two types of skin Appendages microscopic anatomy of the skin hairs sweat glands. Sebaceous glands color of the skin nails. 2. Functions of the skin temperature regulation sense perception mechanical protection water balance The two types of skin The skin can be divided into two classes: (i) the thin skin, and (2) the thick skin.The thick skin is found in the sole and palm of the hand; all other skin are thin skin. Characteristics, by which the thick skin differs from the thin skin are: the thick skin is - (i) more thick than the thin variety, the layer called stratum corneum (horny layer) being particularly thick,(ii) the thick skin contains no hair and no sebaceous gland in persons accustomed to walk barefooted, the skin of the sole may be as thick as 1 cm or so, whereas the skin on the upper eyelid may be as thin as 0. 5 mm only. Appendages of the skin The epidermis of the skin develops from the ectoderm of the fetus. This ectoderm, while developing into the skin ectoderm, may develop into nails, hairs, sebaceous glands and sweat glands. These structures are collectively called the 'appendages' of the skin. Microscopic anatomy of the skin From a physiological point of view, the term skin should include three layers, viz (i) epidermis, (ii) dermis, and (iii) the subcutaneous tissue. Some physiologists, indeed, have used the term skin in this way.* Classical histologists, however, include only the epidermis and the dermis in the skin (the subcutaneous tissue is thus excluded). In this book, the term skin will be used in the sense a classical histologist uses, because, as this author believes, this is the most popular usage. The skin, therefore, consists of two layers: (i) tha epidermis and (ii) the dermis. *Hellier, F. F : <>, in Bell, G. H., Emslie - Smith D, and Patterson, C. R. Text Book of Physiology. ELM. 10th Ed. Churchil, 1980 chap. 17 The epidermis (fig. 8.5.1) consists of 5 layers which are: stratum corneum stratum lucidum. stratum granulosum. stratum spinosum (or prickle cell layer) stratum geriminatirvum (the deepest layer of epi dermis) Fig. 8.5. 1. Microscopic features of skin The cells of the stratum germinativum (= the layer which generates, i. e. generates new cells) continuosly produce new cells (by mitotic division); these cells move continuously towards the surface side and on the way receive a special material, called , ultimately when the superficial most surface is reached, the cells become dead and highly keratinized and constitute the stratum corneum: Stratum germinativum cells are columnar and stand on the basement membrane. The basement membrane stands between the epidermis and the dermis. Stratum spinosum (prickle cell layer) is several (3 to S) cells thick, the individual cells have a prickly (thorny) appearance (and hence the name). The prickled appearance is due to the fact that cytoplasmic processes come out from the individual cells to meet their fellow cytoplasmic strands of the adjacent( cells. Stratum granulosum is about 3 cell layers thick and lies superficial to the prickle cell layer. Although the mechanism of synthesis of keratin is rather complicated, it may be (rather crudely) stated that the cells of the stratum granulosum (=the granular layer) are very important for keratin synthesis. The precursors of keratin take the shape of granules which are present within the cells of the stratum granulosum from which the name has been derived. Stratum lucidum, when present, is found in between the str. granulosum and sir. comeum (Fig. 8. 5.1). it is, when stained by hematoxylin and eosin, rather a clear (lucidum = clear) layer. Str. lucidum is found only in thick skin. When the granules of the str. granulosum are converted into eleidin, the cells become rather clear and form str. lucidum. Eleidin is precursor of keratin. Stratum corneum (comeus =