Lecture Seven Flashcards
What is excretion, regulation of blood volume & pressure and regulation of solute concentration in blood as functions?
-Excretion
o Blood is filtered through the kidneys complex system whereby urine is formed by modification of the filtrate via the reabsorption of required molecules and elimination of waste products
-Regulation of blood volume and pressure
o Control the extracellular fluid of the body by producing either a small volume of concentrated urine or large volume of dilute urine
-Regulation of the solute concentration in the blood
o Major ion concentrations are regulated
-E.g. Na+ , K+ , Cl- , Ca2+
What is regulation of pH levels of the extracellular fluid, red blood cell synthesis and synthesis of vitamin D as functions?
-Regulation of pH levels of the extracellular fluid
o Secretion of H+ to assist with maintaining correct acidity
-Regulation of red blood cell synthesis
o Kidneys secrete erythropoietin, which stimulates the production of red blood cells
-Regulation of the synthesis of Vitamin D
o Vitamin D is required for calcium absorption from the intestines
o Kidneys play a major role in regulating the blood Ca2+ levels not just through its reabsorption but by activating vitamin D
Where do the kidneys lie?
- Lie either side of the vertebral column on the posterior abdominal cavity wall
- T12-L3
- The liver is superior to the right kidney thus it lies slightly lower than the left
- Kidneys are surrounded by several layers
What are the layers of the kidneys?
- Renal capsule - layer of fibrous connective tissue
- Layer of adipose tissue
- Renal fascia – layer of connective tissue
- Final layer of adipose tissue
What is the hilum and the renal sinus?
-Hilum – opening for the
o Renal artery and nerves to enter
o Renal vein and ureter to exit
-Renal sinus is the cavity which opens after the hilum
o Filled with connective and adipose tissue
-Kidney is made up of an outer cortex and inner medulla
What are the renal pyramins, papillae, minor & major calyces, renal pelvis, ureters and renal columns?
-Renal pyramids o Base form the boundary between cortex and medulla Renal papillae o Point of the pyramids Minor calyces o Renal papillae extend into this funnel o N = 8-20 Major calyces o Several pyramids minor calyces merge into major calyces o N = 2-3 Renal Pelvis o Major calyces merge to form Ureter o Renal pelvis forms a small diameter tube the ureter which extends to the bladder Renal columns o In between renal pyramids
What are the nephrons?
- Functional units of the kidneys
- 1.3 million in each kidney
What are the four components of a nephron?
- Renal corpuscle – filters blood
- Proximal convoluted tubule (PCT) – returns filtered substances back to blood
- Loop of Henle (nephron loop) – conserve water and solutes
- Distal convoluted tubule (DCT) – additional wastes added to filtrate
What is the collecting and papillary duct?
Collecting duct
-Connects to several DCT and carries fluid from cortex to medulla and empties into the papillary duct
Papillary duct
-Empties into the minor calyx
What is the flow of urine through the kidneys?
- Renal corpuscle
- Proximal Convoluted Tubule (PCT)
- Loop of Henle (descending limb then ascending limb)
- Distal convoluted Tubule (DCT)
- Collecting Duct
- Papillary Duct
- Minor Calyx
- Major Calyx
- Renal Pelvis
- Ureter
- Urinary Bladder
- Urethra
What is the renal corpuscle comprised of?
-Comprised of;
o Glomerulus – network of capillaries which receives blood from the afferent arteriole and exits at the efferent arteriole
o Bowman’s capsule – capsule that surrounds the glomerulus and where fluid is filtered into from the capillaries and then flows to the PCT.
-Filtration membrane allows fluid to flow into the capsule (first major step of urine formation).
What are the Juxtaglomerular cells, Macula densa and Juxtaglomerular apparatus?
- Juxtaglomerular cells – smooth muscle cells forming an arrangement around the afferent arteriole at the entry point to the glomerulus
- Macula Densa – between the afferent and efferent arteriole lies a section of the DCT which in this section contain specialised cells
- Juxtaglomerular apparatus – the contact of the juxtaglomerular cells and Macula Densa.
What is the function of the Juxtaglomerular Apparatus?
-Function = secretes renin (enzyme) which assists with the regulation of blood pressure and formation of filtrate
What is the proximal convoluted tubule?
- Longer than the DCT
- Outer basement membrane with simple cuboidal epithelial cells
- Inner surface has many microvilli projections
What is the loop of henle?
- Thick portions are simple cuboidal epithelium cells
- Thin portions are simple squamous epithelium cells
What is the distal convoluted tubule?
- Simple cuboidal epithelium cells
- Smaller cells than the PCT
- Less microvilli
What is the collecting duct?
- Simple cuboidal epithelium cells
- Larger in diameter compared to the rest of the renal tubule
In the renal corpuscle what is filtration, tubular reabsorption and secreation?
- Filtration: The process of non-selectively forcing small molecules and water out of the blood into the Bowman’s capsule where it is called filtrate
- Tubular Reabsorption: The process of returning water and solutes back into the blood as the filtrate flows through the renal tubule
- Tubular Secretion: The movement of drugs and toxic by-products from the blood into the filtrate
- Movement of substances are either active or passive, similar to that of reabsorption
What does the endothelial layer, what is the basement membrane and what is a podocyte?
Capillary endothelial layer: o Contains many pores (fenestrations) Basement Membrane o Has spaces between fibbers Epithelial layer- Podocyte o Has foot processes creating filtration slits
What is the renal fraction and the glomerular filtration rate?
-Renal fraction = % of total cardiac output that enters the kidneys
o Resting, healthy adults = 21%
-Glomerular Filtration Rate (GFR) = the amount of filtrate (plasma) that enters the Bowman’s capsule
