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work in progress.... this is half of the urinary system I'll complete it tonight

urinary system

production, storage, elimination of urine in which the kidney filters 125mL/ min of which only 1 mL is excreted as urine per minute. This system contains paired kidneys and ureters, and unpaired bladder and urethra.

kidney

this organ is enveloped by a thin capsule of connective tissue, with an outer cortex, inner medulla, 3 million nephrons, and a hilium

hilium

portal of entry for nerves, blood, and lymph vessels

the upper part of the ureter expands to form...

the renal pelvis, three major calyces, several minor calyces

urine

formed by filtration of plasma in the nephron

Pathway of blood

abdominal aorta->renal arter-> afferent arterioles->glomerulus->efferent arterioles->peritubular capillaries-> renal vein ->inferior vena cava

pathway of urine

bowman's capsule-> proximal convoluted tubule-> loop of henle-> distal convoluted tubule -> collecting tubules and ducts -> calyx

renal cortex consists of

mainly renal corpuscles, proximal convoluted tubules, and distal convoluted tubules

renal medulla consists of

10-18 medullary pyramids. The base sends medullary rays in the cortex while the apex is in contact with the minor calyx

where is urine emptied?

urine travels down each nephron until it's emptied into the CALYX

nephron

functional and anatomical unit with part in the cortex and part in the medulla that consists of renal corpuscle (glomerulus)-> proximal convoluted tubule->loop of henle-> distal convoluted tubule -> collecting tubule and ducts

renal cortex

superficial layer of kidneys consisting primarily of renal corpuscles and convoluted tubules with renal columns of Bertin and medullary rays

Renal columns of Bertin

extensions of cortical tissue that run between adjacent renal pyramids

medullary rays

groups of straight tubules that extend from base of each renal pyramid from base of each renal pyramid

renal corpuscle

tuft of capillaries (glomerulus) surrounded by bowman's capsule

two layers of bowman's capusle

visceral (internal) and parietal (external) with urinary space in between

two portals (poles) of renal corpuscle

VASCULAR where afferent arterioles enter and efferent exit and URINARY where urine that was filtered from the capillaries (between the visceral and parietal layers of bowman's capsule) exit towards the proximal convoluted tubule

visceral epithelium (podocytes)

cell body and many primary processes -> secondary processes (pedicles which are in contact with capillary basal lamina) these cells CAN contract

filtration slits

spaces between pedicles that are bridged by a 6 nm-thick membrane

Basal lamina

~0.1 um thick composed of fused podocyte and endothelia laminae

glomerular basement membrane

contains TWO lamina lucidae and ONE lamina densa, it's the physical and electric barrier between blood in the capillary lumen and the urinary space in capsule, filtration occurs along hydrostatic pressure gradient, opposed oncotic pressure of plasma, and net filtration pressure at afferent end is about 15 mmHg

lamina lucida

also known as lamina rara has fibronectin

lamina densa

has a network of Col IV and laminin in a negatively charged matrix (heparan sulfate)

How does glomerular filtrate different from plasma?

there are NO PROTEINS. Glomerular filtrate crosses through fenestrations in the endothelial cells, through basal laminal and between the "feet" of podocytes to reach the urinary space

parietal epithelium

simple squamous that becomes simple cuboidal at the urinary pole

visceral epithelium (podocytes)

envelope the glomerular capillaries.

What's in between the two layers of bowman's capsule?

urinary space that is emptied into the proximal convoluted tubule

Glomerular capillary wall

contains fenestrated endothelial cells with no diaphragm and mesangial cells

mesangial cells

are located in between capillaries, are contractile controlling capillary lumen, have angiotensin II receptors (-GFR), ANP receptors (vasodilation), and synthesize supportive matrix

proximal convoluted tubule

drains bowman's capsule, reabsorbs from filtrate ALL the glucose, amino acids, small proteins and 80% of the sodium chloride and water, Hydrogen goes, bicarb stays, secretes into filtrate organic wastes such as creatine and urea with numerous ATPase pumps for active transport

tubular reabsorption

important materials that leaked into filtrate (urine) are taken up by PCT cells-> back to circulation via peritubular capillaries

tubular secretion

waste material still in the efferent->peritubular capillaries-> actively secreted into the proximal convoluted tubules

renal tubular secretion

tubular secretion is the transfer of materials from peritubular capillaries to tubular lumen mainly by active transport. This is the major excretion method for drugs and other toxins

proximal convoluted tubule

parietal layer of the bowman's capsule becomes the cuboidal lining of this and is also surrounded by peritubular cappilaries (continuation of efferent afteriole)

90% of reabsorption of filtrate

occurs in the proximal convoluted tubule

descending loop

lined by simple cuboidal epithelium with brush border similar to PCT.. becomes THIN limb with squamous epithelium

ascending limb of henle's loop

lined by cuboidal epithelial cells with few microvilli, impermeable to water-hypotonic urine, ends in distal convoluted tubule

distal convoluted tubule

shorter and wider than the proximal convoluted tubule lacking brush border, aldosterone present, reabsorbs sodium ions from filtrate, moves potassium, ammonium and hydrogen ions into fitrate, contains macula densa

macula densa cells

tall, narrow, closely packed with epithelial cells of distal convoluted tubule that monitor osmolarity and fluid volume in distal convoluted tubule and transmit this info to JG cells via gap junctions

JG cells

modified smooth muscle cells that exhibit characteristics of protein-secreting cells that exhibit characteristics of protein-secreting cels, located primarily in the wall of the afferent arteriole, synthesize renin and store it in secretory granules

Mesangium

interstitial tissue between glomerular capillaries composed of mesangial cells of an amorphous extracellular matrix elaborated by these cells. These cells phagocytose large protein molecules and debris that may accumulate during filtration or in certain diseased states, cells can contract to decrease surface area available for filtration, basement membrane absent

collecting ducts

not part of the nephron, has cuboidal epithelium, with ADH to reabsorb more water to concentrate urine, have segments in both the cortex and medulla, converge to form larger and larger collecting ducts then papillary ducts

Ducts of Bellini (papillary collecting ducts)

large collecting ducts formed from converging smaller ones, lined by simple epithelium composed of columnar cells with a single cilium, empty urine at area cribosa of medullary pyramid into a minor calyx

excretory passages

include minor and major calyces and renal pelvis located within each kidney, the ureter, urinary bladder and urethra located outside the kidneys, possesses three-layered wall composed of a mucosa of transitional epithelium lying on a lamina propria of loose connective tissue, a muscularis and an adventitia

ureter

located between the renal pelvis and the urinary bladder, lined with transitional epithelium, thick, two layered muscular layer, the distal one-third of this structure has an additional smooth muscle-> peristaltic waves throughout that propel urine to enter bladder in spurts

urinary bladder

lined with transitional epithelium whose morphology differs in the relaxed (empty) and distended states, thin lamina propria of fibroelastic connective tissue, and a three-layered muscularis

epithelium of relaxed bladder

5-6 layers thick, rounded superficial cells that buldge into the lumen giving the lumen a scalloped contour, cells contain unique plaques in their plasma membrane and flattened elliptical vesicles in their cytoplasm

epithelium of distended bladder

only has 3-4 layers thick with squamous superficial cells when plaques align and new membrane is added from cytoplasmic vesicles, has a larger luminal surface area than relaxed bladder (reduced number of cell layers)

urethra

moves urine from bladder to outside, has a two-layered muscularis consisting of an inner longitudinal and outer circular layer of smooth muscle, surround at some point by an external sphincter of skeletal muscle which permits its voluntary closure

male urethra

divided into prostatic, membranous, and spongy (cavernous) portions, lined by transitional epithelium in prostatic portion and by pseudostratified columnar or stratified epithelium in other two portions

glands of Littre

mucus-secreting glands

female urethra

lined with primarily stratified squamous epithelium with patches of pseudostratified columnar epithelium, much shorter, easier for upstream transmission of infection, membranous only, may contain glands of Littre in the lamina propria

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