Urinary system

Kidneys

S: Paired organs, reddish, bean-shaped organs


1. Renal capsule with outer layer of dense collagenous connective tissue and inner layer of myofibroblasts
2. Parenchyma
3. calyces
4. Renal pelvis

F: regulate body fluid composition


1. blood filtration
2. electrolyte balance
3. hormone production \[renin, erythrogenin, prostaglandins (E series), hydroxylation of vitamin D\]

L: below the rib cage, on either side of the spine

Renal capsule

S:


1. outer layer = dense collagenous connective tissue
2. inner layer = myofibroblasts → control intrarenal pressure
3. hilus

F: forms connective tissue covering of the sinus and walls of the calyces and renal pelvis, myofibroblasts may aid in resisting volume and pressure variations that can accompany various kidney functions

L: kidney

Parenchyma

S: cortex = outer layer, darker color; medulla = inner layer, light color; lobes; lobules

F:

L:

Cortex

S: outer layer; darker color (contains 90-95% of blood)


1. nephrons


1. renal corpuscles
2. convoluted and straight uriniferous tubules
2. collecting tubules
3. medullary rays (of ferrein)

L: parenchyma of kidney

Renal corpuscle

S: spherical

F: filtration

L: constitute the beginning segment of the nephron

Medulla

S: inner layer; lighter color (contains 5-10% of blood)

F: regulate concentration of the urine

L: kidney

nephrons

S: renal corpuscles=filtration units, convoluted and straight portions of the uriniferous tubules

F: basic functional unit of the kidney

L: cortex of the kidney

collecting tubules

S: walls of the tubules are composed of microvilli, as well as ciliated cells

F: collect filtrate from several nephrons, collect urine from the distal convoluted tubules and carry it into the collecting duct system

L: cortex of the kidney

medullary rays (of Ferrein)

S: appear as vertical striations between nephron-rich regions, contain straight portions of uriniferous tubules and collecting tubules

F: each medullary ray is an aggregation of straight tubules and collecting ducts; conduction of water, minerals, and other organic substances

L: cortex of the kidney

Pyramids

S: conical structures, consisting of:


1. straight tubules of nephrons
2. accompanying straight blood vessels = vasa recta
3. collecting tubules
4. collecting ducts (of Bellini)
5. papilla

F: maintain proper balance of alt and water in the blood

L: medulla of the kidney

renal columns (of Bertin)

S: cortical tissue

F: formation of pyramids

L: extends around the pyramids into the medulla of the kidney

Lobes

S: composed of a pyramid (medullary tissue) + the overlying cortex ; number of pyramids = number of lobes

F:

L: Kidney

Lobule

S: consists of all of the nephrons that drain into a single collecting

F: constitutes the renal secretory unit

L: kidney

Minor calyx

S: cup-shaped structure, lined by transitional epithelium

F: collect urine flowing from the ducts of Bellini and funnel it into the major calyces

L: kidney

Major calyx

S: funnel-shaped structure, branches to form the minor calyces, lined by transitional epithelium

F: collects urine from the minor calyces, serve as intermediate passageways for urine

Renal pelvis

S: funnel shaped structure, lined by transitional epithelium

F: forms the head of the ureter, branches to form the major calyces, collects urine and funnels it into the ureter

L: located in the hilus

Ureters

S: one per kidney, thin muscular tube


1. mucosa


1. transitional epithelium
2. lamina propria - dense collagenous connective tissue
2. muscularis


1. inner longitudinal
2. outer circular
3. third, outer longitudinal layer appears at terminus
3. adventitia = loose connective tissue

F: transport urine to the bladder via peristaltic contraction, conducts urine from the renal pelvis to the bladder

L: kidney

Bladder

S:


1. mucosa - transitional epithelium & lamina propria
2. muscularis - layers (inner longitudinal, outer circular, outer longitudinal)
3. adventitia- covers most (loose c.t.)
4. serosa (covers upper portion)- loose connective tissue and mesothelium

F: stores urine, expel urine by muscular contraction

Urethra

S:

F: transports urine from the bladder to outside of the body, controls the release of urine via a sphincter muscle

Urethra (Female)

S: short = 5 cm, transitional epithelium, pseudostratified columnar epithelium, stratified squamous epithelium; glands (paraurethral and periurethral)

F: outlet for urine from the bladder to the external orifice

L: runs from the bladder to the vestibule of the vagina

Urethra (male)

S: long = 20 cm


1. prostatic urethra (transitional epithelium)
2. membranous urethra (pseudostratified columnar epithelium)
3. Penile urethra (lined by pseudostratified columnar epithelium)

F: outlet for urine from the bladder to the external orifice

L: extends from the bladder through the penis

Renin

S: hormone

F: controls blood pressure, catalyzes conversion of angiotensinogen to angiotensin I

Erythrogenin

S: hormone

F: regulates RBC production, released in response to hypoxia or low oxygen levels, converts blood erythropoetinogen to erythropoietin)

Vitamin D

S: a prohormone

F: completes biochemical process begun in the kidney, regulates calcium homeostasis

Renal corpuscles

S: glomerulus, bowman’s capsule, vascular pole, urinary pole

F: filtering units, site where the primary plasma filtrate is produce from the blood

L: component of the nephron

Glomerulus

S: unique capillary network, capillary tuft, pores, covered by a basal lamina

F: hydrostatic pressure forces water and solutes out through the pores

L: ventral region of the renal corpuscle in the cortex of the kidney

Bowman’s capsule

S: two layers of epithelial cells separated by the urinary space: parietal layer and visceral layer

L: renal corpuscle of the nephron of the kidney

Parietal layer of bowman’s capsule

S: outer boundary of the capsule, composed of a simple squamous epithelium, nuclei bulge into the urinary space, surrounded on the outside by a basement membrane

Visceral layer of bowman’s capsule

S: podocytes, mesangial cells

Podocytes

S: principal cell type, epithelial cells, key feature = thick basal lamina = glomerular basement membrane

F: give rise to elongated branching processes that interdigitate = pedicels (foot processes)

L: glomerulus

Glomerular basement membrane

S: thick basal lamina, fusion of the podocyte basal lamina and the endothelial basal lamina

F: acts as a filter to prevent the passage of higher molecular weight solutes from leaving the blood, allows water and lower molecular weight solutes to pass into the urinary space, polyanions (e.g. heparin sulfate) in the laminar rare impede the passage of cations from the blood

L: kidney

mesangial cells

S: phagocytic cells derived from smooth muscle

F: secrete extracellular matrix → mesangium, keep the GBM clean, structural support for the glomerulus

L: inside of the glomerular basement membrane (GMB), at the vascular stalk and between the glomerular capillaries

Urinary space

S: bowman’s space, urinary sinus

F: collection of filtrate

L: space in between the two epithelial cell layer of bowman’s capsule

Vascular pole

S:

F: site where the afferent arteriole enters and the efferent arteriole exits the glomerulus

L: located on the opposite side of the corpuscle from the visceral pole

urinary pole

S: the simple squamous epithelium of the parietal layer is continuous with the simple cuboidal epithelium of the proximal convoluted tubule

F: site at which the uriniferous tubule connects to the renal corpuscle

L: kidney

Uriniferous tubules

S: selectively reabsorbs 99% of plasma filtrate

F: site where the primary filtrate is concentrated into urine

Proximal convoluted tubule

S: simple cuboidal to low columnar epithelium, prominent brush border of microvilli, extensive interdigitations of the later cell membranes, numerous elongated mitochondria

F: receives primary filtrate from the renal corpuscle, reabsorbs 80% of the volume of the primary filtrate, amino acids and sugars selectively reabsorbed, proteins and particles are endocytosed and digested

L: nephrons of kidneys

Henle’s loop

1. proximal straight segment of Henle’s loop
2. thin segment (thin limb) of Henle’s loop
3. distal thick segment of Henle’s loop

Proximal straight segment of Henle’s loop

S: thick descending segment, pars recta, cuboidal simple epithelium, short brush border of microvilli

F: ion transport

L: kidney

thin segment (thin limb) of Henle’s loop

S: hairpin loop of variable length, depending on the location in the cortex, thin to thick simple squamous epithelium, no blood

F: control of salt and water balance

L: kidney

distal thick segment of Henle’s loop (thick ascending segment, pars recta)

S: similar to distal convoluted tubule; straight tubule; wall of large cuboidal cells; few, short microvilli; extensive basal membrane folds associated with numerous large mitochondria → striations; indistinct lateral cell boundaries; apical nucleus → may bulge into the lumen

F: ion transport

L: medulla and medullary rays of the cortex of the kidney

distal convoluted tubule (pars convoluta)

S: coiled tubule; wall of large cuboidal cells; few, short microvilli; extensive basal membrane folds associated with numerous large mitochondria; indistinct lateral cell boundaries; apical nucleus that may bulge into the lumen

F: reabsorption of sodium/ secretion of potassium; reabsorption of bicarbonate/ secretion of protons → acidification of urine; conversion of ammonia to ammonium; formation of the juxtaglomerular apparatus

L: in cortex of the kidney

juxtaglomerular apparatus

S: macula densa, juxtaglomerular cells, extraglomerular mesangial cells

F: maintain blood pressure and act as a quality control mechanism

L: located at the vascular pole of every glomerulus

arched collecting tubules and connecting tubules (short)

S: simple, high squamous to cuboidal epithelium with distinct lateral cell boundaries

F: collects urine and transports it

Straight collecting tubules

S:

F: concentration of urine

L: located in the medullary layer of the cortex of the kidney

Cortical collecting ducts

S: simple, cuboidal epithelium with distinct lateral cell boundaries, formed by merger of straight collecting tubules, increase in diameter with increasing distance into the medulla

F:

L: located in the medullary rays of the cortex and continue into the medulla of kidney

Papillary duct of Bellini

S: formed by merging of collecting ducts, wall = columnar epithelium, with cells becoming increasingly taller with distance in the medulla

F: drains several nephrons

L: located in the lower portion of the medulla of kidney

Renal papilla

S: area cribosa = perforated epithelium of the surface of the papilla, penetrated by papillary ducts

F: marks termination of the renal tubules and the beginning of the excretory passages

L: apex of a pyramid, where the papillary ducts terminate

Renal artery

S: enters at the hilus

F: supplies blood to a kidney and its nearby adrenal gland and ureter

L: kidney

Interlobar arteries

S: extend along the outer boundaries of the pyramids to the level of the cortex, then branch

F: blood supply to renal capsule

L: kidney

Arcuate arteries (arciform arteries)

S: characteristic arched appearance

F: course over the curved bases of the pyramids at cortical-medullary boundary

L: kidney

Interlobular arteries

S: relatively straight perpendicular branches of the arcuate artery; extend radially into the car

F: blood supply to glomerular capillaries

L: kidney

Stellate arteries

S: star-shaped appearance → radial branches of the distal end of the interlobular arteries

F: supplies blood to the capsule

L: located beneath the capsule, kidney

Capsular capillaries

S: network of capillaries

F: supplies blood to the capsule

L: located in the capsule of kidneys

Stellate veins

S: drain the capsular capillaries near the capsule, drain into interlobular veins

F: supplies blood to the capsule

afferent arterioles

S: lateral branches of the interlobular arteries

F: supplies blood to the glomeruli and uriniferous tubules of the outer portion of the cortex

Glomerular capillary tuft

S: tuft of capillaries

F: source of the primary plasma filtrate (primary urine)

L: located within Bowman’s capsule, kidney

Peritubular capillaries

S: network of capillaries surrounding the uriniferous tubules in the cortex, wrap around the urine tubules

F: drain into stellate arteries and intralobular veins

L: kidney

Nephron

S: renal corpuscle and uriniferous tubules

F: functional unit of the kidney

L: kidney

vasa recta

composed of red blood cells

Myofibroblast

S:

F: aids in resisting volume and pressure variations