BIOL 215 Exam 4 (Liberty University)

main functions of kidneys

-blood filtration/excretion

-regulation

-synthesis of vitamin d

organs that make up the urinary system

kidneys, ureters, urinary bladder, and urethra

describe the renal capsule

made of fibrous CT, surrounds each kidney, + is cushioned by perirenal fat

describe the renal fascia

thin layer of loose CT + anchors kidneys and surrounding adipose to abdominal wall

describe the hilum of the kidney

renal nerves + arteries enter, renal vein + ureter exit, and opens into renal sinus

regions of the kidney

-cortex: outer area

-medulla: inner area (renal pyramids)

-calyces: minor and major funnels

-renal pelvis: enlarged chamber that acts as a funnel to carry urine from calyces to ureter

define nephron

functional and histological unit of the kidney

what makes up a renal corpuscle

glomerulus and bowman's capsule

describe the glomerulus

-network of fenestrated capillaries

-surrounded by bowman's capsule

-afferent arteriole (leads into glomerulus)

-efferent arteriole (leads out of glomerulus)

what percentage of cardiac output is routed to the glomerulus

about 21%

describe the bowman's capsule

-surrounds glomerulus

-parietal layer: simple squamous epithelium

-visceral layer: podocytes

what is the renal tubule comprised of

-PCT (in cortex)

-LoH (mostly medulla)

-DCT (in cortex)

difference between juxtamedullary and cortical nephrons

-85% of nephrons are cortical

-15% of nephrons are juxtamedullary

describe the purpose of the juxtaglomerular apparatus

-BP regulation

-renin production

-filtrate formation

describe juxtaglomerular cells

-ring of smooth muscle cells around afferent arteriole

-contract in response to stretch and sympathetic stimulation

-synthesize, store, and release renin

describe the macula densa

-specialized tubule cells of the DCT

-responds to changes in NaCl

-signal juxtaglomerular cells to release renin

what are the principal factors that influence filtration in the kidneys

renal fraction, renal blood flow rate, renal plasma flow rate, filtration fraction, + glomerular filtration rate

define renal fraction

part of total cardiac output that passes through the kidneys (~21%)

define renal blood flow rate

amount of blood that flows to the kidneys per minute (cardiac output x renal fraction)

define renal plasma flow rate

renal blood flow rate x fraction of blood that is plasma (55%); 650mL/min

define filtration fraction

part of plasma that is filtered into lumen of Bowman's capsules (19%); ~125mL

define glomerular filtration rate (GFR)

amount of filtrate produced each minute; 125mL/min; 180,000mL/day

what are the two auto-regulation mechanisms involved in filtration

-myogenic mechanism

-tubuloglomerular feedback mechanism

describe the myogenic mechanism

-"muscle produced"

-senses minor fluctuations in BP @ glomerulus

-stretch receptors in arterial smooth muscle cells detect changes in BP

-if arterial BP is elevated, smooth muscle in arteries contract, helping limit blood flow into the glomerulus

-if arterial BP falls, smooth muscle in arteries relax, helping increase blood flow into the glomerulus

describe the tubuloglomerular feedback mechanism

-responds to secondary changes in glomerular BP; senses changes in filtrate flow/osmolality in DCT

-changes in filtrate flow are sensed by cells of the macula densa, which then signal the juxtaglomerular apparatus

-afferent arteriole constricts in response to increased BP (detected as increased filtrate flow)

-afferent arteriole relaxes in response to decreased BP (detected as decreased filtrate flow)

what percent of filtrate volume is reabsorbed

99%

describe the process of reabsorption in the proximal tubule involving passive Na+ transport

Na+ enters PCT cell across apical membrane by diffusion (often in symport with another molecule)

describe the process of reabsorption in the proximal tubule involving active Na+ transport

Na+ is pumped across basal membrane into the interstitial fluid; this maintains low Na+ concentration inside PCT cell

describe the general process of reabsorption in the PCT

solutes diffuse across apical membrane + is pumped across basal membrane into the interstitial fluid and then move into the peritubular capillaries

describe the process of reabsorption in the LoH involving the descending thin segment

-primarily water absorption

-highly permeable to water

-moderately permeable to solutes

-water moves out of loop; volume of filtrate reduced by 15%

describe the process of reabsorption in the LoH involving the ascending vasa recta

-water diffuses IN

-solutes diffuse OUT

describe the process of reabsorption in the LoH involving the ascending thin segment

-primarily solute reabsorption

-NOT permeable to water

-permeable to solutes

-solutes diffuse out of the tubule and into the more dilute interstitial fluid

describe the process of reabsorption in the LoH involving the descending vasa recta

-water diffuses OUT

-solutes diffuse IN

describe the process of reabsorption of Na+ in the distal tubule

-Na+ diffuses from filtrate into cells of DCT and collecting duct due to concentration gradient

-Na+ actively transported out of tubule cells into interstitial fluid with Cl-

describe the process of urine concentration

-water reabsorption is regulated by ADH

-in the presence of ADH, water moves by osmosis FROM the DCT and collecting duct INTO interstitial fluid

how do solutes move across the apical membrane in reabsorption

-symport

what are the three ways solutes can move across the basal membrane in reabsorption

-facilitated diffusion

-active transport

-symport

define facilitated diffusion

channels are specific for ion/nutrients

define active transport

ATP required to move solute across membrane

define symport

non-specific channels for ion/nutrients; uses concentration gradients for diffusion

how does water move across the apical and basal membranes in reabsorption

osmosis

why is urea recycled

urea flows in a cycle to maintain a high urea concentration in medulla of kidney

describe the urea recycling process

-descending LoH is permeable to urea > urea diffuses IN from interstitial fluid

-ascending limbs and distal tubules are impermeable to urea

-collecting ducts are permeable to urea > most urea then diffuses OUT into interstitial fluid before it can be excreted into the renal papillae and calyces

what substances are moved during tubular secretion & how are they moved

-H+, K+, drugs, metabolic products, & para-aminohippuric acid (PAH) = actively secreted into renal tubule

-ammonia = diffuses into tubule lumen

what is the purpose of secretion of H+ into tubules

aids in regulation of blood pH

what is ammonia

toxic product of protein catabolism

describe the purpose of the countercurrent exchange mechanism

allows kidneys to concentrate urine

what are the 3 main factors of the countercurrent exchange mechanism

1. parallel tubes:

-loop of henle

-vasa recta

2. fluid flows in opposite directions

3. passive exchange of solute and water

-exchange occurs between blood + interstitial fluid

-requires solute concentration

what role does the descending loop of henle play in the countercurrent exchange mechanism

-water flows OUT and is picked up by vasa recta (water exchange)

-medulla must maintain a high solute gradient in order to draw water out of the descending limb

-solutes become more and more concentrated as filtrate approaches the bend in the loop

what role does the ascending loop of henle play in countercurrent exchange mechanism

-solutes diffuse across apical membrane of LoH cells

-solutes are actively transported across basal membrane in interstitial fluid to keep concentration gradient high

-excess solutes are picked up by vasa recta (solute exchange)

how does atrial natriuretic peptide hormone (ANP) influence the concentration and volume of urine

-produced by right atrium of heart when blood volume increases, stretching cells

-causes vasodilation of afferent arteriole

-increases GFR

-increases filtration surface area

-inhibits renin release

-inhibits Na+ reabsorption and ADH

-increases volume of urine produced: fluid elimination decreases BP

-venous return is lowered, volume in right atrium decreases

how does the renin-angiotensin-aldosterone system influence the concentration and volume of urine

-sensitive to changes in BP

-decrease in BP in the afferent arteriole is sensed by juxtaglomerular cells

-activates renin secretion

-aldosterone increases Na+/K+ pumps in basal membrane; this increases Na+ reabsorption; water follows by osmosis, increasing BP

how does the antidiuretic hormone influence the concentration and volume of urine

-sensitive to changes in blood osmolality

define renal plasma clearance

-volume of plasma cleared of a specific substance each minute

-used to calculate renal plasma flow

-used to determine how much of a substance (urea, glucose, drugs) are cleared from the body

-normal: 70mL/min for urea; 0mL/min for glucose

why is insulin used to estimate GFR through plasma clearance

????

define tubular load

total amount of substance that passes through filtration membrane into nephrons each minute

define tubular maximum

maximum rate at which a substance can be actively reabsorbed

describe the ureters

-bring urine from renal pelvis to urinary bladder

-mucosa: transitional epithelium

describe the urinary bladder

-expandable muscular organ

-muscosa: transitional epithelium

-muscularis: detrusor muscle

-trigone: triangular area between ureters and urethra

describe the male urethra

-extends from the inferior part of the urinary bladder to the external urethral orifice

-internal urinary sphincter: elastic CT and smooth muscle located at bladder outlet; controlled by ANS

describe the female urethra

-shorter urethra

-opens into vestibule anterior to vaginal opening

describe the external urinary sphincter

skeletal muscle surrounds urethra as it extends through pelvic floor; controlled voluntarily by frontal lobe of cerebral cortex

functions of reproductive system

1. production of gametes (sperm & egg cells)

2. fertilization (diploid zygote develops into embryo)

3. development and nourishment of new human being

4. production of reproductive hormones

what are the two layers of the testes

tunica albuginea & tunica vaginalis

describe the structure of the testes

-tunica albuguinea:

-fibrous CT

-forms capsule and separates testis into lobules

-seminiferous tubules:

-site of sperm development

-empty into epididymis

what is the endocrine function of the testes

-leydig cells (interstitial cells)

-secrete testosterone

what is the exocrine function of the testes

secretes sperm

describe the process of spermatogenesis

-takes ~74 days

-spermatozoa produced in seminiferous tubules

-sperm cells mature in epididymis

-begin as germ cells (spermatogonia)

-primary spermatocytes (formed by mitosis of germ cells)

-secondary spermatocytes (formed by meiosis I)

-spermatids (formed by meiosis II)

what is the acrosome of sperm

contains enzymes

what is the head of the sperm

contains nucleus

what is the mid piece of sperm

contains mitochondria

what is the flagellum of the sperm

aids in movement

describe the structure of the penis

3 columns of erectile tissue: corpora cavernosa + corpus spongiosum

-prepuce covers glans

describe the corpora cavernosa

-erectile tissue of dorsum and sides

-form crus/crura

describe the corpus spongiosum

-ventral erectile tissue

-forms bulb

-extends to form glans penis

describe seminal vesicles

-located next to ductas deferentia

-empty into ejaculatory duct

-contain CT and smooth muscle

-produce ~60% of semen fluid

-secretes fructose + citric acid (supports sperm cell metabolism)

-secretes fibrinogen (causes mild coagulation)

describe the prostate gland

-glandular and muscular tissue

-surrounds and empties into prostatic urethra

-secretes thin, milky secretion, alkaline pH

-secretes clotting factors, fibrinolysin

describe the bulbourethral glands

secretes alkaline mucus into spongy urethra just before ejaculation

examples of male diploid and haploid cells

-diploid: spermatogonium, primary + secondary spermatocyte

-haploid: secondary oocyte + ovum

examples of female diploid and haploid cells

-diploid: oogonium, primary oocyte

-haploid: secondary oocyte, ovum

list the ducts of the male reproductive system

epididymis, ductus deferens, spermatic cord, + ejaculatory duct

describe the epididymis

-comma shaped, on posterior of testis

-site of final sperm maturation (12-16 days)

-stereocilia: increase surface area to facilitate absorption of fluid

-sperm moves from the efferent ductules into the duct of the epididymis

describe the ductus deferens (vas deferens)

-passes from epididymis into abdominal cavity

-ampulla: enlarged distal end of ductus

-smooth muscle walls exhibit peristalsis

describe the spermatic cord

contains: ductus deferens, testicular artery, venous plexus, lymphatic vessels, + nerves

describe the ejaculatory duct

-ampulla of ductus deferens merges with duct of seminal vesicle

-extends into prostate gland; opens in urethra

hormones that effect male reproductive system & their functions

-human chorionic gonadotropin: stimulates secretion of testosterone by fetal testes

-GnRH: increases LH + FSH

-FSH: formation of sperm

-LH: Leydig cells secrete more testosterone

describe effects of testosterone on males during puberty

-enlargement and differentiation of male genitals and reproductive duct system

-sperm cell formation

-descent of testes

-hair growth

-increased melanin, skin is rougher and coarser

-increased rate of secretion of sebaceous glands

-hypertrophy of larynx

-increased metabolic rate

-increased RBC count

-increased protein synthesis

-rapid bone growth and closure of epiphyseal plates

describe development of the oocyte

-begins as germ cells (oogonia)

-forms into primary oocyte > undergoes meiosis I

-forms into secondary oocyte > undergoes meiosis II

-if fertilized: becomes a zygote > completes meiosis II

describe the primordial follicle

-present before birth

-contains primary oocytes

-granulosa cells: convert androgens to estrogen (target of FSH)

describe the primary follicle

-develops at puberty from primordial follicle

-contains primary oocyte

-zona pellucida forms around oocyte

-granulosa thickens; cells become cuboidal

-secretes estrogen

describe the secondary follicle

-fluid-filled vesicles appear among granulosa

-theca interna (capsule) forms outside granulosa; synthesizes hormones

describe the mature follicle

-antrum forms from fusion of fluid-filled vesicles

-secondary oocyte surrounded by cumulus cells

-appears as a lump on surface of ovary

-ruptures at ovulation

-releases secondary oocyte

-cumulus cells become corona radiata

describe uterine tubes

-transport oocyte/zygote from ovary to uterus

-infundibulum opens to peritoneal cavity

describe the fimbriae of the uterine tubes

fingerlike folds surround ovary during ovulation

describe the ampulla of the uterine tubes

location of fertilization; longest portion of uterine tubes

describe the mucosal layer of the uterine tubes

-simple ciliated columnar epithelium with longitudinal folds

-provides nutrients for oocyte/pre-embryo through the tube towards uterus

describe the muscular layer of the uterine tubes

-peristaltic contractions help propel fluid/oocyte/pre-embryo towards uterus

what are the three layers of the uterus

-perimetrium: serous membrane

-myometrium: smooth muscle (thickest layer in the body)

-endometrium: mucous membrane

what are the characteristics of the endometrium

-basal layer: continuous w/ myometrium

-functional layer: lines uterine cavity

-spiral arteries: supply blood to functional layer

compare the cervix to the uterus

cervix = less contractile than rest of uterus