1. Anatomy and physiology of the urinary system Flashcards
What are functions of the kidneys?
- elimination of waste substances from plasma
- salvage of essential compounds from filtrate
- regulation of ion levels
- maintenance of osmolality
- regulation of plasma volume and hence blood pressure
- production of hormones
What are functional properties of the kidneys?
- heavily vascularised
- receive 25% of the cardiac output
- convert approximately 20% of this plasma to filtrate while retaining cells and protein in the circulation
- all but 1% of the filtrate is absorbed
- entire circulatory volume is filtered and reabsorbed every 30 minutes
Describe the macroscopic appearance of ox kidneys
Lobed appearance + asymmetry
Describe the macroscopic appearance of horse kidneys
Two different shapes
- right is shaped like a heart
- left is shaped like a bean
Describe the macroscopic appearance of pig kidneys
Normal bean shaped
Describe the macroscopic appearance of sheep kidneys
Normal bean shaped
Describe the macroscopic appearance of cat kidneys
Rounder with capsular veins present on the outside of the kidney
Describe the general anatomy of the urinary system
- Right kidney more cranial to left
- adrenal glands cranial and medial to kidney
- split into upper and lower urinary tract
- renal arteries are branches of the aorta, receive 25-30% of cardiac output
Describe the structure of the deeper renal parenchyma
Medulla - subdivided into renal pyramids that have a base and then a narrow apex
- apex of the medullary pyramid is surrounded by one of the funnels formed by the subdivision of the renal pelvis
- subdivision of the pelvis surrounding the apex of the medulla = papilla
What are the renal parenchyma?
Cortex and medulla made up of millions of nephrons (functional units)
Where in the nephron is filtrate produced?
Proximal end of nephron in capsule
What is the renal corpuscle?
First component of the nephron
- consists of glomerulus (tuft of capillaries) surrounded by the Bowman’s capsule
What are podocytes?
Specialised epithelial cells - sit adjacent to epithelium of capillaries (endothelium)
What is the function of the efferent arterioles in the renal corpuscle?
Arterial blood perfuses out of the capillary network + drains from glomerulus via efferent arteriole
- capillaries have a fenestrated epithelium = fairly permeable epithelium
How is the glomerular filtrate produced?
Some components of plasma are filtered from the glomerulus into the space of the Bowman’s capsule
- this is the glomerular filtrate
What is the GFR?
Glomerular Filtrate Rate
- useful measure of glomerular function
- volume of fluid filtered from the glomerular capillaries into the Bowman’s capsule per unit time
What is the function of the endothelial cell processes in the Bowman’s capsule?
Single layer of endothelial cells lining glomerular capillaries (contains fenestrations)
- restricts the passage of blood cells
What is the function of the glomerular basement membrane in the Bowman’s capsule?
Lies between the endothelium and podocytes (non cellular made up of collagen or collagen like proteins in a glycoprotein matrix)
- main filtration barrier
What is the function of the podocytes in the Bowman’s capsule?
Single layer of the visceral epithelial cells lining Bowman’s capsule
- restrict passage of medium sized proteins and phagocytose macromolecules + metabolising macromolecule fragments + returning them to various body compartments
What is the net filtration pressure?
Net total of hydrostatic and oncotic pressures
What is the hydrostatic pressure?
Capsular pressure
- pressure exerted by a fluid
What is the oncotic pressure?
Form of osmotic pressure induced by soluble proteins
What do low levels of albumin in circulation cause?
Problems with circulatory balance
What are the steps in reabsorption in the proximal convoluted tubule (PCT)?
- Filtration by glomerulus
- Obligatory absorption and secretion by proximal tubule
- Generation of osmotic gradient by loop of Henle
- Regulated absorption and secretion by distal tubule
- Regulation of water uptake by collecting ducts
