Anatomy Notes Week 9 PDF

The Urinary (Renal) System 2 kidneys kidney 2 ureters 1 urinary bladder ureter 1 urethra bladder urethra Main Functions: 1. Regulates the volume, pressure, pH, and osmolarity of blood, and the concentration of different ions within the plasma 2. Eliminates wastes  e.g. urea, uric acid, toxins,...

The Urinary (Renal) System 2 kidneys kidney 2 ureters 1 urinary bladder ureter 1 urethra bladder urethra Main Functions: 1. Regulates the volume, pressure, pH, and osmolarity of blood, and the concentration of different ions within the plasma 2. Eliminates wastes  e.g. urea, uric acid, toxins, drugs Anatomy 1. Kidneys peritoneum kidneys  retroperitoneal  right kidney lower than the left  supported and protected by three layers of connective tissue: a) renal (fibrous) capsule – deep b) adipose (perirenal) capsule – middle c) renal fascia – superficial 1 Kidneys Renal hilum – indentation on the medial surface of each kidney  entry/exit point for: i) renal artery ii) renal vein iii) ureter iv) nerves renal artery renal vein ureter Kidneys Internal anatomy cortex renal column medulla a) renal cortex – superficial layer  contains renal columns pelvis that extend through the major calyx minor calyces renal medulla b) renal medulla – formed by the renal pyramids papilla  renal papilla: apex of each renal pyramid pyramid c) renal pelvis  collects filtrate (urine) from the major and minor calyces, the latter of which exits from each renal papillae 2 The nephron – the site of urine formation Functional unit of the kidney  ~1 million/kidney Two components: proximal convoluted tubule peritubular capillaries distal convoluted tubule glomerular glomerulus capsule efferent arteriole afferent arteriole collecting duct i) Vascular elements cortex medulla  two arterioles and three sets* of capillaries ii) Tubular elements  divided into different zones, with each having specific cell types and functions ascending thick nephron loop ascending thin nephron loop descending thin nephron loop vasa recta Nephron classes 1. Cortical nephrons (~85% of total)  corpuscle originates in the superficial cortex  short nephron loop that just dips into the medulla medulla  are encircled by peritubular capillaries 2. Juxtamedullary nephrons cortex  originate deep in the cortex and extend deep into the medulla  important for the production of dilute or concentrated urine  vasa recta (capillaries) run parallel to the nephron loop 3 glomerulus Nephron structure efferent Renal corpuscle (in cortex):  site of blood filtration a) glomerulus – capillary bed (endothelium) afferent  has many fenestrations (pores) between cells glomerular capsule b) afferent arteriole – enters glomerulus  carries blood delivered to the kidney from the renal artery c) efferent arteriole – exits glomerulus  drains into peritubular (of cortical nephrons) and vasa recta capillaries (of juxtamedullary nephrons) parietal layer Nephron structure d) glomerular (Bowman’s) capsule  double-layered ‘cup’ that surrounds the glomerulus visceral layer i) outer (parietal) layer – simple squamous epithelium ii) inner (visceral) layer – octopus-like cells (podocytes) that encircle the glomerular capillaries; have many finger-like projections that form slits between adjacent cells Glomerulus and podocyte cells are separated by a negatively charged basement membrane; together these three layers form a filtration membrane for blood plasma glomerular capillary capillary endothelium basement membrane podocytes 4 Nephron structure proximal convoluted tubule Renal tubules: a) proximal convoluted tubule – in cortex  receives filtrate from glomerular capsule cortex medulla Cells: cuboidal epithelium with dense microvilli  reabsorbs all filtered glucose and amino acids and ~⅔ of filtered water and ions from the renal tubule, which are then returned to the peritubular capillaries  secretes waste products, toxins, and foreign chemicals (e.g. penicillin) from the peritubular capillaries into the lumen of the renal tubule Renal tubules distal convoluted tubule b) nephron loop (‘loop of Henle’)  associated with the vasa recta (juxtamedullary nephrons only) cortex medulla i) thin descending limb  simple squamous epithelium; highly water permeable thick ascending limb vasa recta thin descending limb ii) thick ascending limb  water-impermeable cuboidal epithelium; actively reabsorbs ions (Na+, Cl–, K+) from the filtrate c) distal convoluted tubule (DCT) – in cortex  cuboidal epithelium 5 Renal tubules Juxtaglomerular complex (apparatus) Point of contact between DCT and afferent + efferent arterioles  helps regulate the rate of plasma filtration from glomerulus i) tubular portion – macula densa  modified DCT cells (taller, narrower); monitor filtrate [salt] ii) vascular portion – afferent and efferent arterioles  modified smooth muscle – secrete renin (enzyme/hormone) juxtaglomerular apparatus efferent afferent arteriole DCT macula densa Renal tubules d) collecting ducts – connect nephron to ureter i) principal cells – cuboidal  for water and Na+ reabsorption; variable and dependent on hormonal signals ii) cuboidal intercalated cells; acid-base balance collecting duct  Type A cells: secrete acid (H+) into lumen  Type B cells: secrete base (HCO3-) into lumen renal pyramid Each collecting duct receives filtrate from numerous nephrons and drains into minor calyces at the tip of minor calyx each renal papilla minor calyx major calyx renal pelvis ureter bladder 6 Urinary System 3. Ureters – retroperitoneal ureter Histology: a) mucosa – transitional epithelium (stretches) b) no submucosa bladder transitional epithelium c) muscularis externa – smooth muscle  two layers; three in lower third d) serosa/adventitia longitudinal muscle layer circular muscle layer adventitia Urinary System 4. Urinary bladder – retroperitoneal The openings of the ureters and urethra form a fixed triangle – trigone (no rugae) Histology: trigone a) mucosa – transitional epithelium with rugae* b) no submucosa c) muscularis externa – three layers thick  termed the ‘detrusor muscle’ (contraction = urination) d) adventitia (posterior/inferior); serosa (superior) 7 Urinary System 5. Urethra Unique histology: a) mucosa  transitional (superior)  pseudostratified columnar (mid)  stratified squamous (external opening) b) muscularis externa  a thickening of the detrusor at the base of the bladder forms the internal urethral sphincter (smooth muscle) 5. Urethra As the urethra passes through the urogenital diaphragm it is surrounded by the external urethral sphincter (a ring of skeletal muscle) ♀ – the urethra is short (<5 cm); transports urine ♂ – the urethra is long (>20 cm); transports urine and semen 8 ♂/♀ Reproductive Systems Structures: 1. Gonads  produce gametes and hormones 2. Ducts  transport and store gametes 3. Accessory glands  produce secretions that support the gametes Male Reproductive System Anatomy 1. Gonads (testes)  located within the scrotum (skin + CT)  surrounded by two layers: A) tunica vaginalis – outer (superficial) cover  serous membrane derived from peritoneum B) tunica albuginea – inner capsule of CT  extends inward to divide the testis into lobules (250 to 300 per testis) 9 Male Reproductive System Each lobule contains: i) seminiferous tubules – produce sperm  unite to form rete testis on posterior side of testes The tubule walls are composed of: a) spermatogenic (germ) cells in various stages of development b) sustentacular (Sertoli) cells  extend from the basement membrane to the lumen; have intercellular tight junctions that form a ‘blood-testis barrier’  surround, nourish, and protect developing gametes b) sustenacular (Sertoli) cells  produce testicular fluid (aids sperm transport during ejaculation)  respond to follicle-stimulating hormone (FSH); secrete a protein that elevates testosterone concentration around the spermatogenic cells ii) interstitial endocrine (Leydig) cells – produce testosterone  located in CT between the seminiferous tubules 10 Anatomy 2. Ducts Sperm formed in the seminiferous tubules enters the rete testis, and then a series of ducts: a) epididymis – posterior border of testis  site of sperm storage and maturation (gain ability to swim) b) vas (ductus) deferens  component of the spermatic cord (also contains nerves, blood & lymph vessels, & skeletal muscle)  runs upward into anterior pelvic cavity and loops over the posterior bladder  vasectomy – ligation of the vas deferens; sperm products removed by macrophages 2. Ducts c) ejaculatory duct  formed by the union of the vas deferens and the seminal vesicle duct d) urethra – 3 regions: i) prostatic – runs through the prostate gland ii) intermediate (membranous) – runs through the urogenital diaphragm iii) spongy (penile) – runs through the corpus spongiosum; exits the glans penis 11 Anatomy 3. Penis a) root b) body (shaft) root c) glans penis (enlarged tip) Houses long cylindrical bodies of erectile tissue (with blood sinuses) covered by CT body glans i) corpus cavernosa – paired dorsal bodies  form bulk of the root/shaft ii) corpus spongiosum – midventral root/shaft  surrounds the urethra; also forms the glans Anatomy 4. Accessory glands a) seminal vesicles (paired) – posterior bladder  secrete an alkaline fluid (~60% of semen) containing fructose to nourish the sperm b) prostate gland (single) – inferior to bladder  encircles the prostatic urethra  secretes slightly acidic, milky fluid (~30% of semen) that nourishes and activates sperm c) bulbourethral (Cowper’s) glands (2)  inferior to prostate; within urogenital diaphragm  secretes thick alkaline mucus that neutralizes low pH of urine and lubricates the urethra; 5% of semen 12 Spermatogenesis – occurs within the seminiferous tubules spermatogonia (2n; stem cells derived from yolk sac) mitosis Type B spermatogonia (lose contact with basement membrane) Type A spermatogonia (undifferentiated; remain in contact with basement membrane) 1º spermatocyte (2n) meiosis I two 2º spermatocytes (1n) meiosis II four spermatid (1n) spermiogenesis four spermatozoa (1n) develop flagella and acrosome lose most cytoplasm Spermatozoa structure a) head  nucleus with 23 chromosomes (1n)  covered by the acrosome (modified lysosome); contains enzymes required to penetrate 2º oocyte body head b) body (midpiece)  contains mitochondria – provide ATP for movement c) tail (=flagellum) tail  composed of microtubules  propel the sperm 13 Semen: Sperm and testicular fluid (5%), and secretions from accessory glands (95%)  ~2 to 5 mL released upon ejaculation; 20 to 150 million sperm/mL (<20 million/mL = infertile)  alkaline (pH = 7.2 to 7.6)  provides a transportation medium, nutrients, and protection for the sperm Female Reproductive System Anatomy 1. Gonads (ovaries)  located in the pelvic cavity on the lateral sides of the uterus Histology: tunica albuginea ovarian mesothelium a) ovarian mesothelium (surface epithelium)  = (simple cuboidal) visceral peritoneum b) tunica albuginea – fibrous CT cortex follicles c) ovarian cortex – contains follicles, CT d) ovarian medulla medulla  blood and lymph vessels, nerves, CT 14 Anatomy suspensory ligament mesovarium Supporting membranes: i) ovarian ligaments broad ligament ovarian ligament  anchors ovaries to the uterus ii) suspensory ligaments  anchors the ovaries to the pelvic wall iii) mesovarium broad ligament (=parietal peritoneum)  superior to the ovaries ampulla Anatomy 2. Uterine (Fallopian) tubes isthmus infundibulum a) infundibulum with fimbriae (‘fingers’)  suspended each over ovary; receive oocytes b) ampulla – middle  site of fertilization ovulation before ovulation fimbriae c) isthmus – connects to uterus 15 2. Uterine (Fallopian) tubes Histology: cilia secretory a) mucosa – simple columnar i) ciliated cells  moves oocyte/zygote/morula along the uterine tube ii) non-ciliated secretory cells with microvilli  nourish oocyte/cell mass b) muscularis externa – smooth muscle  contractions aid oocyte/cell mass movement c) serosa (=visceral peritoneum) Anatomy 3. Uterus (womb) a) fundus – superior to uterine tubes b) body – main portion broad ligament c) cervix – inferior, narrow passage round ligament uterosacral ligament  opens to the vagina Supporting membranes: i) broad ligament – parietal peritoneum ii) round ligaments – fibrous CT  attaches the uterus to the anterior body wall iii) uterosacral ligaments – peritoneum  secures the uterus to the anterior sacrum 16 3. Uterus Histology: a) endometrium – mucus membrane i) simple columnar epithelium ii) lamina propria (CT)  stratum functionalis (shed monthly); contains endometrial glands that secrete a nutritive fluid  stratum basalis (permanent) uterine cavity endometrial glands stratum functionalis b) myometrium – muscularis externa  three layers of smooth muscle c) perimetrium – serosa columnar epithelium stratum basalis myometrium  =visceral peritoneum Anatomy 4. Vagina (birth canal) Passageway for sperm and menstrual flow Histology: a) mucosa – thick stratified squamous epithelium and CT  folded into numerous transverse ridges (rugae) b) muscularis externa – two layers  stretches during intercourse, birth c) adventitia – fibroelastic CT 17 adipose Mammary glands suspensory ligament Modified sweat glands – secrete milk nipple Superficial to the pectoralis major and serratus lactiferous anterior muscles duct lobe Anatomy: i) 15 to 25 lobes/breast; lactiferous ducts open to nipple  surrounded by adipose; suspensory ligaments attach lobes to the dermis (superficial) and muscle fascia (deep) alveolar cells ii) each lobe is comprised of many lobules containing glandular lobe (milk-secreting) alveolar cells lobule lactiferous duct alveoli Oogenesis – occurs within the follicles Oogonia (2n; derived from yolk sac) before birth mitosis many oogonia cells differentiate 1º oocyte (2n) meiosis I 2º oocyte (1n) ovulated 1st polar body (1n)* after puberty meiosis II ovum (1n) (if fertilized) 2nd polar body (1n)* *polar bodies = discarded nuclear material 18 Follicle development: a) fetal i) oogonia appear by 11th week; undergo mitosis  ~5 to 7 million formed ii) differentiate to 1º oocytes – by ~12th week  a single layer of flat follicular cells form around the 1º oocytes within the cortex (‘primordial follicles’) iii) meiosis I begins, but stops in prophase I  meiotic arrest continues until puberty  most oocytes degenerate, such that ~1 to 2 million remain at birth and only ~250,000 by puberty b) childhood – ovary functionally inactive Follicle development c) puberty – ovarian cycles begin i) ~1000 follicles begin to develop each cycle  the oocytes enlarge  follicular cells become cuboidal forming 1º follicle ii) FSH secretion by pituitary stimulates follicular cells of 10 to 25 primary follicles to proliferate into granulosa cells forming a 2º follicle which secretes:  estrogen  zona pellucida around oocyte  fluid; creates a space (antrum) within the follicle Theca cells (endocrine) also form around each follicle from surrounding CT cells 19 Follicle development iii) fluid continues to accumulate within a single ‘dominant’ vesicular (Graafian) follicle  the oocyte becomes isolated, but is still surrounded by a layer of granulosa cells – corona radiata  the enlarged follicle balloons out on the surface of the ovary iv) just prior to ovulation, rising [estrogen] triggers secretion of luteinizing hormone (LH) that stimulates:  meiosis I to continue, forming a 2º oocyte; arrests in metaphase II  ovulation of oocyte (and corona) into the peritoneal cavity Follicle development v) the follicle (still in ovary) fills with blood and clots  granulosa and theca cells proliferate forming the corpus luteum, which secretes progesterone and estrogen corpus luteum vi) if no pregnancy, scar tissue forms and the corpus luteum degenerates into a corpus albicans within two weeks  blood FSH (and LH) levels increase, initiating another cycle; ~500 in reproductive lifetime 20