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List 4 functions of the kidneys

1) stability of body fluid composition and volume
2) regulation of body electrolytes through filtration, reabsorption
3) secretion with the formation of urine
4) regulation of blood pressure
5) acid base homeostasis
6) renal hormone production (prostaglandin, renin, erythropoietin)


what is the basic unit of the kidney and what is it made up of

renal lobe made up of cortical cap that sits on a base of the medullary pyramid (papilla)
the papilla branches into the renal pelvis or a calyx


define pelvis and calyx

Calyx = expansion/dilation of a branch or sub-branch of the ureter or a branch of the pelvis
Pelvis = dilation in proximal ureter


List the 4 types of kidneys and examples of animals that display them

1) unilobar - rodents and rabbits
2) multilobar - ox
3) multilobar with fused cortex (no external lobation) - pig
4) multilobar with fused cortex and medulla - dog, cat, sheep, goat, horse


what are some special characteristics of the multiocar cortical and medullary fusion type kidney

- crest (the totally fused part of the medulla around the pelvis)
- pseudopapillae, which look like papillae but have no openings
- calyces are reduced/modified to form recesses (complex extensions of renal pelvis either side of the pseudopapillae)


position of kidney relative to each other

the right usually cranial to left and right usually more tightly anchored to abdominal roof than left, which is somewhat mobile.


what is the hilum and the sinus

○ The hilum is the opening into the sinus at the medial indentation.
○ The sinus is normally filled with fat and surrounds the renal pelvis.


horse kidney shape and what is special about the ox kidney

right heart shape and left bean shape
ox - distinct lobation externally and no pelvis just major and minor calyces


what does the renal cortex lobule comprise of and what are they

1) cortical labyrinth - the substance of a lobule, consists of renal corpuscles and convoluted tubules
- kidney has granular appearance due to presence of renal corpuscles
2) Medullary rays are groups of parallel straight tubules running between the cortex and the medulla


urine flow from the collecting duct to the bladder

flows from collecting duct - papillary duct - papillary foramen - renal pelvis - ureter - bladder


what are the stellate artery and veins

Stellate artery and vein - at the surface of the kidney in some animals which drain into the interlobular veins


what are the vasa recta

blood supply to the medulla
descending vasa recta are arterioles that form capillary networks within the medulla, the capillaries drain into venules which ascend towards the cortex as ascending vasa recta which drain into arcuate veins


what are the two layers of the glomerular capsule

1. Outer layer = parietal epithelium - simple squamous epithelium with relatively think basement membrane
Inner layer = visceral epithelium - podocytes, closely associated with capillaries - the basement membrane separates them


what are the 4 things that make up the renal corpuscle

1) glomerulus
2) glomerular capsule
3) urinary pole
4) urinary space


what forms the filtration slits in the glomerulus

The pedicles of adjacent podocytes interdigitate to form filtration slits.
Filtration membranes span these filtration slits


histology features of the proximal convulted tubule and what is special in the cat

- simple cuboidal epithelium
- cells are large so only a few nuclei per profile and lumen is relatively small
- apical surface has brush boarder (microvilli)
- basal striations with mitochondria between infoldings
- in cats these cells contain lipid which gives yellow colour to cortex


histology features of proximal straight tubule

very similar to proximal convoluted tubule but in dogs have lipid so yellow not cats


histology features of Loop of henle (thin ascending and thin descending)

- simple squamous epithelium
- similar to capillaries but:
1) wider lumen
2) round nuclei (bulge into the lumen)
3) few microvilli and basal striations


histology features of distal straight tubule

same as distal convoluted tubule however can have presence of macula densa cells


histology features of distal convoluted tubule

- simple cubodial epithelium
- lumen larger than PCT
- no brush boarder and no striations
- eosinophilic


histology features of straight collecting tubules

- simple cuboidal epithelium
- centrally located round nucleus
- pale staining cells bulge into the lumen


epithelial layer of the papillary duct and foramina

- epithelium is simple cuboidal/columnar and is continuous with the transitional epithelium lining the urinary pelvis and covering the surface of the medulla


what are the 3 components of the juxtaglomerular complex/apparatus and their main functions

1) macula densa - chemoreceptor for NaCl concentration in tubular lumen
2) juxtaglomerular cells - release renin and involved with contraction and relaxation of afferent arteriole - act as baroreceptor
3) mesangial cells - close contact with macula densa cells act as chemoreceptors, phagocytosis, supportive, contractile


urinary passages (ureter, bladder and urethra) what epithelium and muscle layers

- transitional epithelium - maintain integrity under tension/expansion (expect end of urethra stratified squamous epithelium)
- tunica muscularis - of generally 3 distinct layers of smooth muscle
- inner longitudinal, middle circular, outer longitudinal (except bladder - only one muscular layer)


ureter how enter bladder and how does it propel urine into bladder

- Enters the bladder either side of the midline and passes obliquely through the wall creating a mucosal-flap valve, which prevents reflux of urine into the ureters.
- propels via peristalsis


what are the ligaments involved with stabilisation of the bladder

Two lateral ligaments, one either side extends laterally from the body, near the neck, to the walls.
One ventral ligament lies in the median plane and extends to the floor.


how much blood flow does the nephron use

20% cardiac output


what does the mesangial cells made up of and what they can do

- bundles of microfilaments + contractile proteins in cytoplasm →contractile
→ change filtration slits & fenestrae
→ change Glomerular Filtration Rate (GFR)


what cells produce angiotensin

proximal tubules


what are the functions of the principle cells and intercalated cells in the collecting ducts

1) principle cells
- Reabsorb water and urea (medullary region) through aquaporins - ADH
- Reabsorb Na+ & Cl secrete K+ - Aldosterone
2) Intercalated cells
- Secrete H+ Reabsorb K+