Comparative microanatomy of the Urinary Sytems Flashcards
pars convolute?
convoluted part
renal corpuscles, proximal and distal tubules, peritubular capillaries, and portions of collecting tubules
pars radiata?
collecting tubules and portions of the loops of Henle
medulla of the kidney?
collecting tubules, thick and thin segments of the loops of henle and the vasa recta
regions of the kidney?
cortex
pars convolute
pars radiata
medulla
renal nephrons?
these are the functional units within the kidney - known as nephrons
what does each nephron consist of?
consists of a blood supply and a specialised network of ducts called a tubule
vascular parts of renal nephrons?
include afferent arteriole, glomerulus, efferent arteriole and peritubular capillaries
tubular parts of renal nephrons?
include bowman’s capsule, proximal tubule, loop of henle, distal tubule and collecting duct
the renal corpuscle is made up of?
Glomerulus, Bowman’s capsule and Bowman’s space
what will make the renal corpuscle?
the glomerulus and its epithelial covering together make the renal corpuscle
once the ultrafiltrate is formed - what happens in the renal corpuscle?
the fluid enters Bowman’s space
Bowman’s space?
the space between the capillary tuft and Bowman’s capsule
How many parts does the Bowman’s capsule have?
has two parts - parietal (squamous epithelial cells) and visceral layer (podocytes)
where does blood enter the glomerular tuft?
ENTERS via the afferent arteriole at the vascular pole and leave via efferent arteriole
afferent and efferent arteriole by the glomerular tuft - where are they located?
these two vessels are immediately adjacent to one another at the vascular pole, which is at the opposite end of the glomerulus from the urinary pole
how can the efferent and afferent arteriole control how much blood flows into the glomerular tuft?
they can contract and dilate - changing the amount of blood that flows into the glomerular tuft
what does each nephron begin with?
each nephron begins with a blind expansion that is invaginated by a cluster of capillaries known as glomerulus
what is the glomerulus?
it is a complex web of capillaries derived from the afferent arteriole
where can glomeruli be located?
in the cortex of the kidney or the corticomedullary junction
what does the glomerulus do?
it filters blood to produce a fluid, called filtrate
the major structures of the glomerular filtration barrier include?
endothelium/pores, glomerular basement membrane (basal lamina) and podocytes
describe the structure of the glomerular endothelial cells?
they are fenestrated
what is another important feature of the endothelial cells - apart from being fenestrated?
the other important feature is the glycocalyx - which covers the luminal surface of the cell
what does the glycocalyx do?
it provides the building block needed for a strong and functional vascular endothelium
it also filters out negatively charged molecules, leukocytes, red blood cells, platelets and larger proteins
what is the glomerular basement membrane?
it is a product of the fusion of the basement membrane produced by endothelial cells and podocytes
describe the distal convoluted tubule?
it has smaller cells with less cytoplasm, which gives the impression of ‘more nuclei’ in cross section Lack brush border microvilli
Made up of simple cuboidal epithelium
JGA?
(next to the glomerulus)
juxtaglomerula apparatus
what does the JGA include?
macula densa, juxtaglomerular cells, mesangial cells
what does the JGA do?
it controls the rate of the glomerular blood flow depending on various factors such as hydration, blood volume and ion concentration
what are macula densa cells?
these are sensitive to sodium chloride; reduced levels lead to vasodilation, prostaglandin secretion causes renin secretion
what is the macula densa?
it is a short segment of the distal convoluted tubule that is next to the afferent and efferent arterioles
how do the macula densa cells (modified smooth muscle cells) allow the release of renin?
they sense sodium chloride concentration in the lumen and stimulates the juxtaglomerular cells to synthesise and release renin into the bloodstream
where are juxtaglomerular cells within?
between the macula densa and the vascular pole
macula densa?
this is a modified smooth muscle cell lining the afferent arteriole that can contract or relax in response to the macula densa
horse urine?
foamy urine
horse pelvis contains mucus glands
renal pelvis epithelium?
transitional epithelium
structures that make up the major filtration barrier?
slit pore diaphragm
glomerular basal membrane
podocyte foot process
endothelial cell from the renal glomerulus
fenestrate or endothelial cell pore
where are renin containing vesicles found?
in juxtaglomerular cells
Extraglomerular mesangial cells?
a type of smooth muscle cell, they play a role in autoregulation of blood flow to the kidney and regulation of systemic blood pressure through the renin-angiotensin system
Juxtaglomerular apparatus?
a structure in the kidney that regulates the function of each nephron
what cells make up the Juxtaglomerular apparatus?
extraglomerular mesangial cells
what are intraglomerular mesangial cells involved with?
vasoconstriction
and phagocytosis
histologically, what is beneath each capillary loop in the kidneys?
there are 2 to 3 mesangial cell nuclei beneath each capillary loop
what constitutes the mesangium?
the mesangial cells and the glomerular extracellular matrix collectively constitute the mesangium
what are podocytes?
they are specialised epithelial cells
where are podocytes located?
located on the abluminal surface of the capillary loop
podocytes have numerous processes, give examples?
like tentacles that surround the capillaries
foot processes of podocytes?
(FP) of podocytes
these are devoid of organelles except microtubules/microfilaments
foot processes of podocytes?
these wrap around the glomerular capillaries to form the filtration slits
in epithelial cell in inner layer of Bowman’s capsule
what do podocytes foot processes compose?
a functioning slit diaphragm (SD) in between a meshwork of proteins actively participating in podocyte signalling
what do podocytes do?
they support glomerular capillaries and are part of the glomerular filtration barrier
what is the filtration barrier made up of?
endothelial cells/pores, basal lamina, podocytes - slit pores (slit diaphragm) between podocyte foot processes
what do podocytes respond to?
to hormones and growth factors that are present in the circulation
what cells do podocytes work with?
work with mesangial cells to support the structure and function of the glomerulus
what does the urinary system do?
filtration, resorption, secretion and concentration
describe the proximal convoluted tubule:
it has abundant dark-pink cytoplasm (mitochondria) with prominent brush border (microvilli)
highly infolded basal cell membrane
simple columnar epithelium
describe the loop of Henle:
loop of henle, thick descending portion resemble PCT
thin segment with simple layer of squamous epithelium
thin ascending portion; epithelial cells resemble the distal convoluted tubule
describe the papillary duct-terminal portion of collecting tubule:
it is lined with simple columnar or pseudostratified epithelium
describe the collecting tubules of the urinary system:
collecting tubules
no active reabsorption
simple cuboidal epithelium without brush border
what apparatus is lying just outside Bowman’s capsule and the glomerulus?
the juxtaglomerular apparatus (JGA)
describe the histology of the fish kidney:
unusual glomerular appearance and renal system
interstitial cells have endocrine and haematopoietic function
No loops of Henle
Fresh water fish - few, small glomeruli
describe histology of bird kidney:
cortical tissue dominates
two types of nephrons (most nephrons do not contain a loop of henle)
medullary type nephrons?
mammalian type and less numerous and it has loop of henle
cortical type of nephron?
(reptilian) type and has plenty (more numerous nephrons) and it lacks loop of henle
located entirely in the cortex
