Structure and function of the glomerulus

-maintain water balance -maintain salt balance -maintain blood pH -excretion of metabolic waste products -blood glucose regulation - regulating blood pressure and kidney function (renin) -stimulating red blood cell production (erythropoietin) -metabolise vitamin D into its active form

What are the (8) functions of the urinary system?

-constriction of afferent arteriole -decreases flow into glomerulus -decreases filtration

What happens to filtration rate when there is an increase in systemic blood pressure?

-dilation of afferent arteriole -increases flow into glomerulus -increases filtration

What happens to the filtration rate when there is a decline in systemic blood pressure?

passive process in which hydrostatic pressure forces fluids and solutes through a membrane

What is glomerular filtration?

local adjustment of blood flow to individual organs based on their immediate requirements suppresses changes in renal blood flow and glomerular filtration rate in response to mean arterial pressure from 80 to 180 mmHg

What is intrinsic regulation (also known as autoregulation?)

macula densa- closely packed specialised cells lining the distal tubule wall to the glomerulus. Monitor salt concentrations to regulate renal blood flow

What is the black box?

podocyte- prevent plasma proteins from entering urinary ultrafiltrate

What is the blue box?

network of small capillaries at the beginning of a nephron in the kidneys first stage of filtering process of blood carried out by the nephron in its formation of urine

What is the glomerulus?

afferent arteriole

What is the green box?

juxtaglomerular cells- secrete renin

What is the grey box?

specialised pericytes (cells that wrap around endothelial cells lining capillaries) that participate indirectly in filtration by contracting and reducing the glomerular surface area and filtration rate (in response mainly to stretch)

What is the mesangium in the glomerulus?

the property of smooth muscle cells to adapt to systemic blood pressure

What is the myogenic mechanism in intrinsic regulation of glomerular filtration?

proximal convoluted tubule

What is the orange box?

renal nerve- regulate renal blood flow, glomerular filtration rate, tubular reabsorption of sodium and water, release of renin and prostaglandins

What is the white box?

-capillaries lined by endothelial cells containing fenestrae (pores) to allow for filtration of fluid, plasma solutes, protein -basement membrane consisting of proteins, collagen, agrin and nidogen which are synthesised and secreted by endothelial cells and podocytes. -podocytes which are cells lined with folds of cytoplasm called pedicles. These control filtration of proteins from the capillary lumen into Bowman's space

Describe the lining of the glomerulus

the factors that influence perm-selectivity are the negative charge of the basement membrane, the podocytic epithelium and the effective pore size of the glomerular wall. large and/or negatively charged molecules will pass through less frequently than small and/or positively charged molecules large negatively charged proteins cannot filtrate easily so their concentration increases as plasma is filtrated. This increases osmotic pressure (induced by proteins) along the length of the glomerular capillary

Describe the permeability of the glomerulus

Macula Densa (MD) cells respond to filtrate NaCl concentration (which varies directly with filtrate flow rate). When GFR increases, there is not enough time for reabsorption and the concentration of NaCl in the filtrate remains high. MD cells respond to high levels of NaCl in filtrate by releasing vaso- constrictor chemicals (ATP and others) that cause intense constriction of the afferent arteriole, reducing blood flow into the glomerulus. This is drop in blood flow decreases GFR, slowing the flow of filtrate and allowing more time for filtrate processing (NaCl reabsorption). The low NaCl concentration of slowly flowing filtrate inhibits ATP release from MD cells, causing vasodilation of the afferent arterioles. This is allows more blood to flow into the glomerulus, thus increasing GFR.

Describe the tubulo-glomerular feedback cycle in the regulation of glomerular filtration