Histology and Human Development Lecture 17 PDF

Unified Lecture 17 GENITOURINARY HIHD-211 TERM-3 Basic Science Department COSHP, KSAU-HS, KSA Learning Outcomes By the end of this lecture, the student should be able to: 1. Identify the histological features of the G.U. tract in general 2. Recognize the structure of the kidney, ureter, urinary blad...

Unified Lecture 17 GENITOURINARY HIHD-211 TERM-3 Basic Science Department COSHP, KSAU-HS, KSA Learning Outcomes By the end of this lecture, the student should be able to: 1. Identify the histological features of the G.U. tract in general 2. Recognize the structure of the kidney, ureter, urinary bladder, and urethra. 3. Describe the histological organization of the testis and the process of spermatogenesis in the germinal epithelium of the seminiferous tubule 4. Describe the structure of the prostate gland, and structure of male urethra 5. Describe the structural changes that occur in the endometrium of the uterus over the course of a menstrual cycle. 6. Describe the histological features of the uterine tube and its wall. 7. Identify different parts of the ovary and describe the progression of follicular development in the ovary from the primordial stage to ovulation. The Urinary System Comprises Of: ▪ Two kidneys ▪ Two ureters ▪ A urinary bladder & a urethra FUNCTIONS: ▪ Removal of nitrogenous wastes ▪ Maintenance of water, electrolytes and acid-base homeostasis ▪ Regulation of osmotic concentration of blood (osmoregulation) ▪ Endocrine function: kidney produces hormones, like: ▪ ▪ renin ▪ erythropoietin Kidney converts vitamin D to its active form LO-1,4 The kidney is a main functional organ of the urinary system LEARNING OUTCOMES The kidney is invested by a tough fibrous capsule (Cp) and by a thick layer of perinephric fat Renal cortex (C) forms a smooth outer zone which extends down between the pyramids as renal columns Renal medulla (M) is made up of multiple medullary pyramids separated by extensions of the cortex, the renal columns The apex of the pyramid (renal papilla P) opens in a funnel-shaped minor calyx Hilum (H) is the site of entry and exit C cortex,Cp capsule H hilum,M medulla, P papilla,U ureter of the renal blood vessels and the ureter LO-3 THE NEPHRON ▪ ▪ ▪ 1. 1. A nephron is the functional and structural unit of the kidney Each kidney consists of about 1 million nephrons A nephron comprises of two components Renal corpuscle + Renal tubule LO-3 Dr. Ismail Memon The Renal Cortex In a histological slide the renal cortex is easily identified even at low magnification by the presence of renal corpuscles (G), which are absent in the renal medulla However, the bulk of the cortex is occupied by the proximal and distal convoluted tubules (T) The arcuate arteries and veins help to demarcate the cortex from the medulla LO-3 Dr. Ismail Memon The Nephron - RENAL CORPUSCLE The Glomerulus: ▪ A network of anastomosing capillaries that invaginates Bowman's capsule ▪ The capillary loops are invested by the visceral layer of Bowman's capsule called podocytes (visceral epithelial cells) ▪ The spaces between the capillary loops are filled by basement membrane-like material called mesangium Bowman's capsule: ▪ is a blind end of the renal tubule ▪ consists of a single layer of flattened cells resting on a basement membrane ▪ Visceral layer is reflected around the vascular stalk to become continuous with the parietal layer LO-2,3 The parietal epithelium of Bowman's capsule is continuous with the epithelium lining of renal tubule The space between the two layers is known as Bowman's space Space is continuous with the lumen of the renal tubule Dr. Ismail Memon Renal Corpuscle ▪ Afferent arteriole: Supplies the glomerulus ▪ Efferent arteriole: Drains the glomerulus ▪ Vascular pole: where afferent & efferent arterioles enter and leave the corpuscle. It is situated opposite the urinary pole ▪ Urinary pole: where Bowman's space continues into renal tubule LO-3 Renal Corpuscle A – Afferent Arteriole B – Efferent Arteriole C – Bowman’s Capsule Epithelium-podocytes (visceral layer) D – Capillary Endothelium E – Glomerular basement membrane F – Beginning of Proximal Convoluted Tubule LO-3 Dr. Ismail Memon Renal Corpuscle - The Filtration Barrier ▪ The filtration barrier is situated between the capillary lumen and Bowman's space ▪ It is made up of: ▪ capillary endothelium ▪ glomerular basement membrane (common basement membrane between endothelium & podocytes) ▪ Podocytes LO-2,3 Dr. Ismail Memon KIDNEY - The Nephron RENAL TUBULE The proximal convoluted tubule (PCT) ▪ Longest & most convoluted part of the tubule. 65% of the reabsorption occurs here ▪ Confined to the renal cortex and make up the greater part of its bulk ▪ Histology: The lumen of the PCT is lined by the simple cuboidal epithelium with prominent brush border (BB) of tall microvilli. The cytoplasm of the cells stains dark pink due to a high number of mitochondria ▪ Basement membranes stain blue by this technique (Azan Stain) LO-3 Dr. Ismail Memon KIDNEY - The Nephron RENAL TUBULE The loop of Henle ▪ It is a continuation of PCT ▪ It dips down into the medulla, where it loops back and returns to the cortex to its own renal corpuscle, becoming the first part of the distal convoluted tubule It includes: ▪ Distal straight part of the proximal tubule ▪ Thin descending limb & thin ascending limbs: lined by Simple Squamous Epithelium ▪ Thick ascending limb: lined by low cuboidal epithelium LO-2,3 Dr. Ismail Memon KIDNEY - The Nephron RENAL TUBULE The distal convoluted tubule (DCT) ▪ It is a continuation of the thick ascending limb of the loop of Henle after its return to the cortex ▪ Histology: The lumen of the DCT is lined by the simple cuboidal epithelium ▪ DCT lacks a brush border and have less cytoplasm than those of the PCT ▪ The collecting tubule (CT) ▪ Histology: The lumen of the CTs is lined by the simple cuboidal epithelium ▪ The nuclei of the CT cells lie close to the luminal surface and tend to bulge into the lumen ▪ Several collecting tubules converging to form a collecting duct LO-2,3 KIDNEY - The Nephron RENAL TUBULE The collecting ducts ▪ Lined by simple tall columnar epithelium ▪ Descend through the cortex & merge in the medulla to form the large ducts which discharge urine into the pelvicalyceal system LO-3 Dr. Ismail Memon Epithelial Lining of a Renal Tubule PART OF TUBULE TYPE OF EPITHELIUM Proximal Convoluted Tubule Simple cuboidal with prominent brush border Thin Limb Loop Of Henle Simple squamous Thick Limb Loop Of Henle Simple cuboidal Distal Convoluted Tubule Simple cuboidal Collecting Tubule Simple cuboidal Collecting Duct Simple columnar LO-2 Dr. Ismail Memon Juxtaglomerular Apparatus (JGA) ▪ JGA regulates blood pressure via the renin-angiotensin-aldosterone mechanism ▪ JGA is made up of three components: ▪ Macula densa: specialized DCT cells where the DCT abuts the vascular pole of the glomerulus ▪ Juxtaglomerular cells of the afferent arteriole (modified smooth muscle cells). Secrete renin ▪ Lacis cells (mesangial cells) LO-2,3 Dr. Ismail Memon THE RENAL MEDULLA It consists of closely packed tubules of two types: ▪ Loop of Henle ▪ Collecting tubules and ducts LO-3 Dr. Ismail Memon URETER The ureters are muscular tubes leaving each renal pelvis carrying urine to the bladder Mucosa ▪ Epithelium: Transitional epithelium (urothelium), thrown up into folds in the relaxed state ▪ Lamina propria: Loose collagenous tissue ▪ Muscle Layer (muscularis propria): Two layers of smooth muscle arranged as ▪ An inner longitudinal layer ▪ An outer circular layer ▪ Another outer longitudinal layer is present in the lower third of the ureter ▪ Adventitia: Loose collagenous tissue containing blood vessels and nerves LO-2,3 Dr. Ismail Memon URINARY BLADDER It is muscular sac that stores and expels urine ▪ Mucosa ▪ Transitional epithelium ▪ Lamina propria: loose connective tissue ▪ Muscularis mucosa: Thin & often incomplete smooth muscle layer ▪ Submucosa: collagenous tissue ▪ Muscularis propria: three loosely arranged layers of smooth muscle (detrusor muscle) and elastic fibers ▪ ▪ ▪ ▪ inner longitudinal middle circular outer longitudinal Adventitia contains arteries, veins and lymphatics LO-2,3 Dr. Ismail Memon Urethra ▪ ▪ Urine leaves the bladder through a tube-like structure called the urethra Urine flow is controlled by two urethral sphincters: The internal urethral sphincter is at the start of the urethra. This sphincter is composed of smooth muscle. The external urethral sphincter is skeletal muscle Histology of the Female Urethra ▪ The urethra in females is short ▪ The lining epithelium of the female urethra is pseudostratified columnar epithelium and stratified squamous epithelium LO-2,3 The male reproductive organs are: ▪ Testes: ▪ ▪ ▪ A duct system: Epididymis, vas deferens, ejaculatory ducts ▪ ▪ Store and conducts the spermatozoa from each testis Exocrine glands: secrete seminal fluid ▪ ▪ ▪ ▪ Production of the male gametes (spermatozoa) Secretion of male sex hormones Testosterone Paired seminal vesicles Prostate gland (single) Bulbourethral glands Penis: an organ of copulation LO-3 TESTIS Each testis is surrounded by: ▪ Tunica vaginalis: an extension of peritoneum. It has visceral and parietal layers separated by serous space ▪ Tunica albuginea: A dense connective tissue layer that lies underneath the visceral layer of the tunica vaginalis. It gives rise to numerous collagenous septae ▪ The septae divide testis is into about 250 testicular lobules Within each lobule there are 1- 4 seminiferous tubules in which spermatozoa are produced The seminiferous tubules converge upon a plexus of channels, the rete testis From the rete testis, 15 to 20 small ductuli efferentes, conduct spermatozoa to the extremely tortuous first part the epididymis LO-3 TESTIS ▪ ▪ Seminiferous tubules are lined by: ▪ Germ cells in various stages of maturation. The basal layer of germinal cells is supported by a basement membrane ▪ Sertoli cells (Non-germ cells): rest on the basement membrane extending to the lumen of the tubule. They support and nourish the developing spermatozoa The interstitium is present between the seminiferous tubules. It consists of: ▪ Leydig cells: endocrine cells occur singly or in groups in between the tubules. They contain eosinophilic cytoplasm & round central nucleus ▪ Leydig cells secrete the Testosterone LO-3 Stages of Germ Cell Development & Maturation S1= Primary spermatocytes S3= Spermatids S4= Small pointed form of permatozoa St= Sertoli cells M= Myofibroblasts LO-3 Prostate gland ▪ ▪ It is a fibromuscular gland that surrounds the bladder neck and the first part of the urethra Histology: Prostate is composed of glandular part and the stroma ▪ Fibromuscular Stroma is mixture of collagenous fibrous tissue and smooth muscle fibres ▪ Glands are lined by tall columnar epithelium thrown up into folds ▪ Corpora amylacea are inspissated (solidified) secretions in glands lumina G: Gland CA: Corpora amylacea St: Fibromuscular stroma LO-3 Urethra Histology of male urethra The urethra in the male is longer than the female Functions as a conduit for the passage of urine and semen The male urethra is divided into three sections: ▪ Prostatic Urethra It is the first portion of the urethra that goes through the prostate gland It is lined by transitional epithelium LO-4 Urethra Membranous Urethra The second part of the male urethra that passes through the pelvic diaphragm The lining epithelium is pseudostratified columnar epithelium Spongy Urethra ▪ The third part of the urethra is also called the penile urethra. It travels through the corpus spongiosum of the penis. The lining epithelium is pseudostratified columnar epithelium which changes to stratified squamous epithelium distally. LO-4 FEMALE REPRODUCTIVE SYSTEM Click to edit Master subtitle style OVARY Functions: ▪ Production and ovulation of oocytes ▪ Production and secretion of hormones Histology Coverings: Germinal Epithelium: Simple cuboidal epithelium (does not produce ova) Tunica Albuginea: Fibrous tissue capsule under the epithelium LO-7 OVARY Ovarian Stroma consists of fibroblasts, collagen fibers & few smooth muscle cells Cortex forms a peripheral zone of the dense stroma. It contains ovarian follicles with female gametes (ova) in various stages of development (Primordial follicles, Secondary follicle, Graafian follicle) & post-ovulatory follicles (corpora lutea, corpora albicantes) Medulla forms the central zone of loose stroma and contains blood vessels and nerves LO-7 Ovarian follicles Fallopian tubes The fallopian tubes carry ova from the surface of the ovaries to the uterine cavity and are also the site of fertilisation by spermatozoa Histology: ▪ Epithelium: simple ciliated columnar ▪ Lamina propria: loose connective tissue ▪ Smooth muscle layers: ▪ inner circular ▪ outer longitudinal ▪ Adventitia ▪ Loose C.T. with blood vessels and nerves. LO-6 Uterus ▪ It is a pear-shaped organ lying in the pelvis. ▪ It is divided into body and cervix. ▪ It is wall consists of three layers : ▪ 1-Perimetrium ▪ 2-Myometrium ▪ 3- Endometrium LO-5 Uterus Divided into: Body and Cervix Histology: Body is composed of ▪ Endometrium (mucosa) of variable thickness depending on the different stages of the menstrual cycle. In women of child-bearing age, the endometrial lining consists of a pseudostratified columnar ciliated epithelium forming simple tubular glands ▪ Only the mucosa of the body of the uterus takes part in the menstrual cycle ▪ Myometrium: Smooth muscles which makes up the bulk of the uterine wall ▪ Perimetrium/Serosa: A layer of simple squamous epithelium that is a continuation of visceral peritoneum LO-5 Uterus ▪ Endometrium (mucosa of the uterus) ▪ It is lined by simple columnar epithelium. ▪ It is rich in simple tubular glands that penetrate deeply and reach the myometrium. ▪ The endometrium consists of 2 zones : ▪ - Stratum functionalae (functional layer ) : is thick layer and sloughed off (removed) at menstruation. ▪ -Stratum basalae (basal layer) : is thin and acts as regenerator layer. LO-1 Uterus ▪ Myometrium : it is thick muscular wall and has a great capacity to elongate. ▪ It consist of bundles of smooth muscle which run in various direction (three layers) 1-Outer layer. 2- Middle (rich blood supply ) 3-Inner (longitudinal arranged fibers) LO-5 The endometrium undergoes marked cyclic change ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ 1- Menstrual phase : Time 3-5 days Shedding off the stratum functionalae 2- Proliferative phase : At this stage the uterine gland increase in length and the endometrium increases in size. functional layer becomes thicker than basal layer during late proliferative phase. 3-Secretory Phase : At this phase the endometrium hypertrophies. glands become coiled and accumulate large quantities of secretory product 4- Premenstrual Phase : Periodic contraction of Blood Vessels lead to necrosis of the endometrium and its glands , then endometrium shrinks in size. Uterine cervix ▪ Its lower part of the uterus and protrudes into the upper vagina and contains the endocervical canal linking the uterine cavity with the vagina ▪ Endocervical Canal “EC” is lined by a single layer of tall columnar mucus-secreting epithelial cells. It forms tubular glands, the endocervical glands ▪ Ectocervix: lined by thick stratified squamous epithelium ▪ The junction “J” between the ecto- and endocervical epithelium is at the external os, here endocervical canal opens into the vagina ▪ The main bulk of the cervix is composed of tough, collagenous tissue containing a little smooth muscle LO-5 Endocervix LO-5 Ectocervix 40