Microanatomy Urinary System

Block 7

Is the urethra longer in males or females

males

in what ways do kidneys function in water and electrolyte homeostasis

filter cellular waste from blood

Selective re absorption of water and solutes

Regulate fluid balance

Maintain electrolyte homeostasis / acid base balance

what 2 hormones do kidneys produce

renin

Erythropoietin

functions of kidneys

water and electrolyte homeostasis

Excrete metabolic waste products, bioactive substances, and excess water

Hormone production

Blood pressure regulation

Activation of vitamin D

How do feline kidneys differ from other species

instead of the cortex and medulla being the same color, the cortex is paler and the medulla is darker in cat kidneys.

This is due to an extra layer of fat / adipose tissue in the kidney cortex of cats.

Where in the kidney does the main artery, main vein, and ureter pass

renal hilus

What other organs have a hilus

spleen, liver, lungs

In what types of animals is it typical to have unilobular kidneys

carnivores

How does the multilobular kidney of large ruminants differ from a multilobular pig kidney

in large ruminants, each kidney lobe is outlined distinctly by deep grooves and it lacks a renal pelvis

In pig, it has a smooth surface instead of the deep groove separations. The cortical portions of the lobes are fused

T/F: carnivore kidneys loves are fused extensively, which gives the unilobular appearance

True

the kidney capsule contains what 3 things

collagen fibers

Smooth muscle

Blood vessels

Renal corpuscles and convoluted tubules are located where in the kidney

cortex

The loop of Henle and collecting duct are located where in the kidney

medulla

a single nephron includes what structures

the cortex and medulla (renal corpuscle, convoluted tubule, loop of Henle, and collecting duct)

What is the functional unit of the kidney

nephron

The pelvis of the kidney is located at the center and contains what 4 features

Urothelium

Submucosa

Smooth muscle

Adventitia

What is the site of osmoregulation in the kidney

nephrons

Nephrons filter water and small molecules from the ___ ____ to form a filtrate

Blood plasma

What gets selectively reabsorbed from the filtrate in the nephron

most of the water and other molecules

What 2 components form the renal corpuscle

glomerulus

Bowmans capsule

What surrounds the glomerulus

bowman’s capsule

List nephron components in order of filtrate passage

glomerulus → proximal convoluted tubule → loops of henle → distal convoluted tubule

is the collecting duct part of the nephron

no

once filtrate has reached what urinary system structure it can be called urine

collecting duct

what type of capillaries are found in the Bowman’s capsule / glomerulus

fenestrated

what type of cells in the parietal layer/epithelim of the Bowman’s capsule

squamous

what is the main function of the glomerulus

protein conservation

where can mesangial cells be found

between fenestrated capillaries in the glomerulus Bowman’s capsule

what filtration steps occur at the vascular pole of the glomerulus

blood entry/exit

blood enters glomerular capillaries through afferent arteriole

blood leaves through efferent arteriole

how does ultrafiltration occur at the glomerulus

blood pushed through filtration barrier and ultrafiltrate enters urinary space

what occurs at the urinary pole of the glomerulus

ultrafiltrate enters the proximal convoluted tubule

what 3 components make up the filtration barrier in the glomerulus

endothelium of glomerular capillary loops with fenestrations

glomerular basement membrane

podocytes with pedicels (foot processes)

T/F: many pedicels of varying sizes extend from cell body and wrap around the glomerular capillaries, interdigitating with other podocytes

true

are podocytes between glomerulus capillaries

no

they SURROUND capillaries

the glomerular basement membrane consists of

fused basal laminae of capillaries and podocytes

what molecules are retained by the filtration barrier and what molecules cross freely

retained - large molecules, albumin

cross freely - small molecules, ultrafiltrate

which structure of the filtration barrier retains albumin

lamina densa of the basement membrane

it is an exclusion barrier for molecules the size of albumin and IgG

what size are filtration slits

25-60nm

during urine formation, the primary filtrate is produced how and where

ultrafiltration of blood

in the glomerulus, which is in the renal corpuscle

like blood plasma, ultrafiltrate does not contain most ______

proteins

during urine formation, how much of the filtrate is reabsorbed

98%

most of the water and Na+ reabsorbed

all glucose and amino acids reabsorbed

during urine formation, tubular secretion includes what molecules

K+, H+, NH4+, bile salts, drug metabolites

what remains in the tubular system and empties into ureter after other molecules are excreted

some water and waste molecules

mesangium

mesangial cells and matrix

T/F: mesangial cells are phagocytic, contractile, and provide support

true

what animal species do not have a glomerulus

deep-sea fish

when there is not a glomerulus present, what surrounds the renal tubule

renal portal system

where does the proximal convoluted tubule begin and where is it found in the kidney

begins at urinary pole of renal corpuscle

found in cortex only

the proximal convoluted tubule contains what cells

single layer of cuboidal epithelial cells with microvilli

are the cells of the proximal convoluted tubule highly metabolically active or minimally

highly

have many mitochondria, require a lot of energy

what gets reabsorbed in the proximal convoluted tubule

glucose, Na+, H2O, amino acids, peptides, low molecular weight proteins

do proximal convoluted tubules have a basement membrane

yes

are cell limits of proximal convoluted tubules distinct or indistinct, and why

indistinct

the lateral borders have interdigitations of the cell processes

what gives proximal convoluted tubules basal striations

the basal surface has a folded membrane

how much of the Na+ and water in the glomerular filtrate are absorbed in the proximal convoluted tubule

85%

why are proximal convoluted tubules a target for nephrotoxins

because they are so metabolically active and therefore sensitive to hypoxia

anions, cations, and urea are selectively reabsorbed where in renal system

proximal convoluted tubule (nephron)

what vitamin is activated by the proximal convoluted tubule

vitamin D

The loop of Henle is U-shaped with multiple segments. Name 3 segments and what cell shape are in the epithelium

thick descending - cuboidal epithelium

Thin segment - squamous epithelium

Thick ascending - cuboidal epithelium

What is the vasa recta

capillary loop that parallels the course of the nephron loops / loop of henle

Facilitates ion & water exchange

The thick ascending segment of the loop of Henle moves into what structure of the nephron

distal convoluted tubule

The distal convoluted tubule has what cells

single layer of cuboidal epithelial cells with basal striations

T/F: distal convoluted tubules have cuboidal epithelial cells with microvilli surface projections

false

No microvilli, the rest is true

What is the site of action of aldosterone

distal convoluted tubule

Where is the macula densa found and what cells does it contain

found in distal convoluted tubule

Specialized chemoreceptor cells

What does the lumen of collecting ducts contain

primitive urine

What shape cells are lining collecting ducts

cuboidal to low columnar epithelium

What is the site of action of antiduretic hormone (ADH) and via what receptor

site of action is collecting ducts

Via aquaporin receptors

What do the collecting ducts connect the distal convoluted tubule to

the renal papillae / crest

Principal cells in collecting ducts reabsorb ____ and ____, while intercalated cells participate in _______

principal cells reabsorb Na+ and H2O

Intercalated cells participate in acid-base balance

The terminal portion of collecting ducts are

papillary ducts

Where do papillary ducts empty

área cribosa of the renal crest or renal papilla (species specific)

What organs have a terminal artery system

kidneys, brain, heart, spleen

T/F: 25% of cardiac output goes through kidney

true

arterial flow through kidney

renal artery → interlobular artery → arcuate artery → interlobular artery → intralobular artery

Between the cortex and medulla, which has more or less intersitium

more - medulla

Less - cortex

the macula densa cells are what type of receptor and what do they sense

chemoreceptors

Sense Na+ concentrations in filtrate

Juxtaglomerular cells are modified _________ cells

smooth muscle

What cells of the juxtaglomerular apparatus detect blood pressure variations as baroreceptors and secrete renin into vessel lumen

juxtaglomerular cells

do Juxtaglomerular cells secrete renin into response to high or low Na+ concentration and high or low blood pressure

low Na+ in filtrate

Low blood pressure

Juxtaglomerular cells secreting renin activates a pathway that promotes what change to Na and H2O retention, leading to what changes in blood pressure

increased retention

Increased blood pressure

What are the 4 layers of tubular organs

Tunica mucosa

Tunica submucosa

Tunica muscular is

Tunica serosa / adventitia

In ureters, how does the tunica submucosa differ from a true submucosa

true submucosa is separated from mucosae (T. Mucosa) by laminate muscularis

Ureters do not have lamina muscularis

Ureters carry urine from where to where

from renal pelvis to bladder

What type of epithelium lines tunica mucosa of ureters and urinary bladder

transitional epithelium, which has cells that flatten when stretched

How many layers of muscle in tunica muscularis

3

What layer of ureter and urinary bladder lining has outer and inner longitudinal layers and a middle circular layer

tunica muscularis

Do ureters have tunica serosa or tunica adventitia as outer layer

tunica adventitia

T/F: the unrianry bladder contains only smooth muscle

false

Has smooth muscle (detrusor muscle), but also skeletal muscle sphincter near urethra

The inner circular layer of smooth muscle in the tunica muscularis is external on the dorsal surface of the foal’s urinary bladder, which allows _______

preferential bulging of the dorsal surface

Creates less resistance

Why is equine urine cloudy

Mucus glands in submucosa layer

What cells line the urethra

initially, transitional epithelium

Then, stratified squamous near the external urethral orifice

Kidney develops from what embryonic origin

mesoderm / mesonephros