Simplified Overview of Urine Formation. Urinary System II Lecture Notes Pages Reproductive System I Lecture Notes Pages

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1 Urinary System II Lecture Notes Pages Reproductive System I Lecture Notes Pages Lecture Overview Urinary System Review/QuestionsUrine formation Reabsorption/Secretion Countercurrent multiplier and water conservation Renin-angiotensin pathway Reproductive System Introduction and Overview Male External anatomy (scrotum/penis) Erection Internal structures Testes Accessory organs (epididymis, vas (ductus) deferens, seminal vesicles, prostate gland, bulbourethral (Cowper s) gland Semen 2 Simplified Overview of Urine Formation Renal corpuscle provides the raw materials to the nephron for processing PCT reclaims those substances the body can use; gets rid of some things DCT gets rid of those substances the body doesn t want or need; reabsorbs some more Na +, Ca 2+ Collecting tubule (duct) provides the OPTION of reclaiming H 2 O or letting it pass out of the body [p ] 3 1

2 Reabsorption/Secretion in Kidney * * * Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 * Keep in mind: Where Na + (or solute, in general) goes, H 2 O and Cl - usually follow. [p. 135] 4 Tubular Reabsorption [p ] Reabsorption by tubular cells is a selective process Diffusion Osmosis Carrier-mediated transport Facilitated diffusion Active transport Co- and counter-transport Occurs mainly in the proximal convoluted tubules (PCT) Has a transport maximum, T m, for most substances besides Na + T m is the rate at which solutes can be transported, e.g., 375 mg/min Renal threshold is the plasma level (concentration) above which a particular solute will appear in urine, e.g., 180 mg/dl Peritubular capillaries are well-suited for reabsorption Low hydrostatic pressure High degree of permeability Higher colloid osmotic pressure due to filtration 5 Reabsorption in PCT [p ] 65% of filtrate volume is reabsorbed in the PCT 8 mm Hg COP Tubular fluid All uric acid, about 50% of urea, and no creatinine is reabsorbed Figure from: Saladin, Anatomy & Physiology, McGraw Hill,

3 Substance Reabsorption in the PCT. Mechanism of Reabsorption Notes Na + (Cl - ) Primary Active Transport Na + reabsorption is the driving force for most other reabsorption H 2 O Osmosis Closely associated with movement of Na + (Obligatory water reabsorption) Glucose Secondary Active transport Limited # of molecules can be handled (T m = 375 mg/min); attracts H 2 0 Amino Acids Secondary Active transport Three different active transport modalities; difficult to overwhelm Other electrolytes Secondary Active transport [p ] 7 Overview of Facultative H 2 O Reabsorption Note that outflow of water from collecting duct is dependent upon the osmotic gradient in the medulla Increasing concentration Urea Under influence of ADH (Facultative water reabsorption) 8 The Loop of Henle (Nephron Loop) [p. 138] Crucial renal function is to keep the body fluids at about 300 mosm (osmolarity of blood plasma) by varying the concentration of urine The mechanism shown is called the countercurrent multiplier SO HOW DOES THIS HELP? Increasing concentration Figure from: Martini, Anatomy & Physiology, Prentice Hall,

4 The Countercurrent Multiplier Recall that all movement of H 2 O occurs passively by osmosis We would like some mechanism to concentrate urine Excrete more H 2 O when body fluids are tending to become hypotonic (more dilute) Excrete less H 2 O when body fluids are tending to become hypertonic (more concentrated) Utilizes two factors Hypertonicity of the peritubular fluid, established by the countercurrent multiplier Variable permeability of the collecting tubules to H 2 O depending upon levels of ADH We will use the phrase, Water follows salt (solute) when it can 10 Vasa Recta of Juxtamedullary Nephrons Recall that the vasa recta is present in juxtamedullary nephron loops (which give the kidneys the ability to produce a concentrated urine) The vasa recta functions to 1. Deliver blood to medullary cells 2. Return reabsorbed solutes and water in the medulla to the general circulation without disrupting the medullary concentration gradient [p. 138] 11 Influence of ADH on H 2 O Reabsorption [p ] Note that amount of water pulled out of collecting duct is dependent upon the osmotic gradient in the medulla that was established by the countercurrent multiplier. Figure from: Hole s Human A&P, 12 th edition, 2010 Urea Under influence of ADH (Facultative water reabsorption) 12 4

5 Summary of Events in the Nephron/Collecting Duct (Aldosterone) (Aldosterone) 1. Filtrate produced 2. Reabsorption of 65% of filtrate 3. Obligatory water reabsorption 4. Reabsorption of Na + and Cl - by active transport 5,6. Facultative reabsorption of water 7. Absorption of solutes and water by vasa recta 13 Some Factors Influencing Salt/H 2 O... Diuretics Increase water loss in urine - Caffeine (coffee, cola, tea); causes dilation of afferent arteriole (effect on GFR?) -Alcohol/narcotics; inhibit ADH (result?) - Antihypertensive drugs, CHF meds; decrease retention of Na+ (result?) - Diabetes mellitus; increased glucose in tubular fluid (result?) -Diabetes inspidus; decrease secretion of ADH [p ] - Addison s Disease; decreased aldosterone secretion (result?) [Mnemonic: Addison ADD SALT] 14 [p. 141] Juxtaglomerular Apparatus Juxtaglomerular cells (JG) - modified smooth muscle cells in the wall of the afferent arteriole that contract (and secrete renin) Cells of the macula densa (MD) are osmoreceptors responding to solute concentration of filtrate MD + JG cells = juxtaglomerular apparatus Figure from: Martini, Anatomy & Physiology, Prentice Hall,

6 Renin-Angiotensin System [p. 141] (ACE) Figure from: Hole s Human A&P, 12 th edition, 2010 Renin is released by the juxtaglomerular apparatus due to: 1) Decline of BP (Renin 1/Pressure) 2) Juxtaglomerular stimulation by sympathethic NS 3) Decline in osmotic concentration of tubular fluid at macula densa ( Renin 1/[NaCl] ) Stabilizes systemic blood pressure and extracellular fluid volume 16 Reproductive System I Lecture Notes Pages Overview of the Reproductive System Produce and maintain sex cells, or gametes ( sperm, ova) Transport gametes and supplemental fluids to appropriate location so that fertilization can occur Development and Birth (Females, in humans) [p. 147] 18 6

7 Male Reproductive System [p. 147] Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Testis Epididymis Vas (ductus) deferens Ejaculatory duct Urethra 19 Male External Reproductive Organs [p. 147] Temperature control Figure from: Martini, Anatomy & Physiology, Prentice Hall, Descent of Testes [p. 147] Descent begins around 7 th month of pregnancy under the influence of testosterone Descent is necessary for sperm production (temp about 3 o C lower than body temp) Failure of testes to descend = cryptorchidism 21 7

8 Scrotum [p. 147] Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 pouch of skin and subcutaneous tissue dartos muscle smooth muscle in dermis; contracts to cause wrinkling of the scrotum (traps heat) medial septum divides scrotum into two chambers each chamber lined with a serous membrane each chamber houses a testis and epididymis Cremaster muscle can retract testes 22 Penis [p. 148] Connection of penis to body wall (root) Parasympthetic stimulation (S4) causes vasodilation and filling of erectile tissues with blood, resulting in erection and compression of veins draining penis 23 Penis [p. 148] Preputial glands in the prepuce (foreskin) produce a waxy material called smegma. This can be a source of bacterial growth if hygiene is poor. Circumcision is the surgical removal of the prepuce. 24 8

9 Structure of the Testis [p ] Rete Testis Epididymis is about 16 FEET in length! Surrounded by the tunica vaginalis and tunica albuginea a tough, white, fibrous capsule that encloses each testicle Septa of albuginea divide each testicle into about 250 lobules Each lobule contains 1-4 highly coiled seminiferous tubules that give rise to sperm Interstitial cells (of Leydig) lie in between seminiferous tubules and secrete male sex hormones 25 Epididymis Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Takes about 2 weeks for sperm to travel through the epididymis - Maintains fluid produced in the seminiferous tubules - Recycles damaged sperm and cellular debris - Store and protects sperm, and aids in their maturation 26 Ductus (Vas) Deferens muscular tube about 45 cm long; transports sperm ( can store sperm for several months) extends from epididymis to ejaculatory duct Figure from: Martini, Anatomy & Physiology, Prentice Hall,

10 Male Internal Accessory Organs - Glands X 2 [p. 150] (1) 28 Seminal Vesicles [p. 151] attached to ductus deferens near base of bladder secretes alkaline fluid (60% of the volume of semen) secretes fructose, prostaglandins, and proseminogelin begins capacitation of sperm contents empty into ejaculatory duct Figure from: Martini, Anatomy & Physiology, Prentice Hall, Prostate Gland [p. 151] surrounds beginning of urethra ducts of gland open into urethra secretes a thin, milky, slightly alkaline fluid (20-35% of semen volume) secretion enhances fluid mobility (PSA) contains seminalplasmin secretes Prostate-specific Antigen (PSA) composed of tubular glands in connective tissue also contains smooth muscle Figure from: Martini, Anatomy & Physiology, Prentice Hall,

11 Clinical Application - Prostate Enlargement benign prostatic hyperplasia occurs in most men over 50 BPH causes frequent urination risk factors include a fatty diet, having had a vasectomy(?), or exposure to certain environmental factors treatments include surgical removal drugs insertion of balloon into urethra freezing of tumor insertion of stent between lobes of prostate to relieve pressure on urethra 31 Bulbourethral (Cowper s) Gland inferior to the prostate gland secretes thick, alkaline mucus - helps lubricate the tip of the penis (glans) and neutralize any urinary acids in urethra fluid released in response to sexual stimulation [p. 150] Figure from: Martini, Anatomy & Physiology, Prentice Hall, sperm cells (spermatozoa) Semen [p ] secretions of seminal vesicles, prostate gland, and bulbourethral glands (seminal fluid) slightly alkaline (offsets acidity of reproductive tract) prostaglandins (stimulates contraction in reproductive tract) nutrients enzymes (protease, seminalplasmin, fibrinolysin) million sperm cells per milliliter (< 20 mil/ml = sterile) usually about 2-5 ml of fluid per ejaculate 33 11

12 Seminiferous Tubules and Sperm Maturation [p. 152] Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Spermatogonium = stem cell 34 Structure of a Sperm Cell [p. 152] Mitochondria Only flagellum in human body Approx 0.06 mm long Enzymes used to penetrate the egg during fertilization 35 Spermatogenesis [p. 152] Spermatogonium (2n) Primary spermatocyte (2n) Meiosis I Secondary spermatocyte (n) Meiosis II Spermatid (n) Spermiogenesis Spermatozoan (n) 36 12

13 Review of Mitosis and Meiosis Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001 [p. 152] Mitosis production of two identical diploid daughter cells *Meiosis production of four genetically varied, haploid gametes 37 Mechanism of Emission and Ejaculation Figure from: Hole s Human A&P, 12 th edition, 2010 [p. 153] Loss of arterial vasodilation -> detumesence - > refractory period 38 Hormonal Control of Male Reproductive Functions hypothalamus controls maturation of sperm cells and development of male secondary sex characteristics negative feedback controls concentration of testosterone 39 13