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Histology / Embryology Unit 4 > Urinary System > Flashcards

Flashcards in Urinary System Deck (66)
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What type of organ is the kidney?

A compound tubular gland which separates metabolic wastes from blood and regulates composition of blood plasma


What covers the outside of the kidney?

A collagenous thin capsule of fibroblasts and myofibroblasts


What are renal corpuscles?

Part of the renal cortex, they include:
1. Capillary glomerulus
2. Bowman's capsule


What is a glomerulus?

Capillary loop derived from afferent arterioles and drained by efferent arteriole


What are renal columns?

Cortical tissue found in the medulla, extending between pyramids


What are medullary rays?

Bundles of tubules in the cortex which extend into the medulla. Contains the proximal and distal straight tubules plus collecting ducts.


What comprises the medulla of the kidney? How is it organized / drained?

Inner portion composed of tubules and collecting ducts.

They group into pyramids, which converge to form a papilla. The papilla has a rounded apex which projects into a minor calyx?


What makes up a kidney lobe and how many are there?

A medullary pyramid and the cortical substance associated with it - 8-18 of these in humans


What makes up a kidney lobule?

A medullary ray (including straight portions of proximal and distal tubules and their collecting ducts) and the cortical tissue associated with it


What is a uriniferous tubule?

The nephron (from bowman's capsule to distal convoluted tubule) + collecting duct


What are the parts of a nephron?

1. Bowman's capsule - blind-ended, indented by glomerular capillary
2. Proximal thick tubule - convoluted and straight
3. Thin limb - descending and ascending
4. Distal thick tubule - straight and convoluted


What are the parts of the loop of Henle?

Proximal straight tubule, descending thin limb, ascending thin limb, distal straight tubule


What are the two types of nephrons and how do they differ? Where are their renal corpuscles?

1. Cortical / subcapsular - renal corpuscles are in outer cortex, with short loops of Henle not reaching farther than outer medulla. They do not concentrate urine significantly.

2. Juxtamedullary - renal corpuscles are in corticomedullary junction. They have long loops of Henle going deep into pyramids to concentrate urine.


What is the path of blood flow from renal artery to glomerulus?

1. Renal artery - enters at hilus
2. Interlobar arteries - run between pyramids
3. Arcuate arteries - interlobar arteries bifurcate at corticomedullary junction to form arteries running between base of pyramid and cortex
4. Interlobular arteries - run radially in cortex between medullary rays
5. Afferent arterioles - from interlobular arteries
6. Glomerular capillaries - from afferent arterioles


What is interlobar vs interlobular arteries?

Interlobar - between pyramids
Interlobular - between medullary rays in cortex


What are arcuate arteries?

They are arteries from interlobar arteries which run at corticomedullary junction between cortex and base of pyramids


What are efferent arterioles and why is their size important?

They accept the blood from glomerular capillaries and drain individual renal corpuscles.

They are smaller than afferent arterioles so that filtration pressure is maintained


What do efferent arterioles in subcapsular glomeruli form? Where do they drain?

Peritubular capillary networks around tubules in the cortex, and then drain into arcuate veins


What do efferent arterioles in juxtamedullary glomeruli form? Where do they drain? Why is this physiologically important?

They form vasae rectae arteriae (straight arteries) into the medulla where they make hairpin turns and ascend as venous vasae rectae and join arcuate veins. This forms the counter-current exchange system.


What is a renal corpuscle and what leaves at its two poles?

Place of filtration for plasma from glomerular capillary, which is fenestrated and branched.

Vascular pole: Site of entry of afferent arteriole and exit of efferent arteriole
Urinary pole: Proximal convoluted tubule


What are the layers of Bowman's membrane and what is it continuous with?

Parietal / Capsular layer: Make outside of Bowman's capsule made of simple squamous epithelial cells
Visceral layer: Partially surround the capillary

Parietal layer is continuous with beginning of proximal convoluted tubule


What does a Bowman's capsule enclose?

Urinary space, which contains provisional urine. Bounded by parietal and visceral Bowman's layers.


What makes up the visceral layer of Bowman's membrane?

Podocytes, which have interdigitating pedicels separated by slit spores spanned by slit membranes


What defines the glomerular endothelium?

Endothelium cells with OPEN fenestrae (no diaphragm) though some have diaphragms also present. Do not allow passage of molecules greater than 70 kD into the glomerular basement membrane


What makes up the glomerular basement membrane (what fused layers + what compounds)?

Fused basal lamina of endothelial cells and podocytes.

Usually appears trilaminar, and contains type 4 collagen, heparan sulfate, laminin, and fibronectin, giving it a negative charge.


What is the function of the negatively charged glomerular basement membrane?

Limits movement of negatively charged proteins which manage to get through the open fenestrae


What is the slit membrane? What protein holds it together?

The membrane between pedicles formed by the adhesion protein nephrin, it has a role in filtration.


What is special about the glycocalyx of podocytes?

It is also polyanionic, to prevent passage of negatively charged molecules into the filtrate


What causes most severe form of glomerular nephritis?

Auto-antibodies to glomerular basement membrane. However, antigen-antibody complexes can accumulate in GBM to produce acute symptoms


What causes congenital nephrotic syndrome and what is the major symptom?

Defect in gene producing nephrin, so the slit membrane doesn't work properly. Children have low albumin in blood but high in urine (it is being lost to the urine filtrate)