Module 9

Ureter

tube that transports from the kidney to the urinary bladder

Urinary bladder

holding structure for urine

Females

bladder is anterior to the uterus and posterior to the pubic bone and anterior to the rectum

Males

connection of the bladder to the prostate which is inferior to the bladder

Distention of bladder

made possible by smooth muscle bands that make up the detrusor muscle

500-600mL

volume of fluid in bladder in adults

Ureteral openings

connect the urinary bladder to the urethra, which empties urine into the external environment

Sphincters

two of them control the passageway from the bladder to the urethra; controlled by reflexes

Too much volume

opens sphincters

Cortical control of external sphincters

allows controlling micturition

Position of kidneys

positioned more superiorly in comparison to ureter and urinary bladder

Right kidney

slightly lower than left as it is slightly displaced by the liver on the right

Function of kidneys

filter the blood in the functional units (glomerulus of the nephrons)

Nephron

supported by several structures in the kidney, embedded in the cortex and medulla and they drain filtrate into minor calyx, major calyx, renal pelvis, and ureter

Renal cortex

superficial, supports nephrons

Renal medulla

less superficial, supports nephrons

Medulla

made up of renal pyramids which are separated by renal columns

Filtrate

urine

Renal hilum

renal nerve, renal artery, renal vein, renal pelvis

Longer nephron loop

extends into the cortex

Nephron composition

glomerulus, proximal and distal convoluted tubule, the nephron loop and collecting duct which drains into the minor calyx

Glomerulus

filtering

Proximal and distal convoluted tubule and nephron loop

secretion and reabsorption)

Renal artery

delivers blood to the kidneys at renal hilum

Blood from renal artery

flows into the segmental artery around the boundary of cortex and medulla and then into the interlobar artery around each pyramid and then into the cortical artery which reaches the glomerulus via afferent arterioles

Afferent arterioles

site of blood filtration, blood arrives at glomerulus at high pressures and is surrounded by the glomerulus filled with podocytes

Podocytes

opening through which the fluid from the blood is filtered into the renal corpuscle and starts flowing through the tubule in the nephron

Filtered blood

exits the glomerulus via the efferent arteriole and drains into peritubular capillaries

Peritubular capillaries

network that surrounds all of the sections of the tubule of the nephron

Vasa recta

specific part of the capillaries around the nephron loop

Fenestration properties

exchange water and salts between the tubule of the nephron and blood (this will determine how much water or salts is in the urine eventually)

Blood leaves kidneys

via the cortical radiate veins, arcuate veins, interlobar veins and then renal vein

Filtrate flows through the tubule space in the nephron

blood flows through the tubule for the final exchange of water and salts

Urine

formed when filtrate collects in the collecting duct and drains into the minor calyx

Blood in capillaries

ends up flowing in the direction opposite to the filtrate in the tubule

Countercurrent flow

opposite direction of flow between the blood and filtrate in the tubule; key to efficient exchange of salts and water between blood in the capillaries and filtrate in the tubule of the nephron

Filtration

first step in urine production

Positive outward pressure in glomerulus

fluids can leave the blood through podocytes of the glomerulus and drain or filter in the recap capsule

Renal capsule

leads into proximal convoluted tubule, then the nephron loop and the distal convoluted tubule and collecting duct

Filtrate travelling through renal tubule

further exchange of ions and water takes place, this determines the final concentration of water and waste in urine

Nutrients and water

can be taken further from the filtrate as it passes through the nephron and reabsorbed back in blood or interstitial space

Wastes that have not been filtered out in glomerulus

can be added later along the tubule so that they leave the body

Darker urine

body was conserving water and not adding too much of water to the filtrate

Renal tubule pH control

more hydrogen ions can be secreted and reabsorbed in the renal tubule space to make adjustment to blood pH

Reabsorption

movement toward blood

Secretion

movement toward space inside the tubule

Nephron loop

most specific reabsorption and secretion key to how much water can be reabsorbed

Descending loop

permeable to water

Ascending loop

permeable to salts

Filtrate movement in nephron loop

opposite direction to blood flow

Favourable concentration gradients of salts

always exist around the nephron loop

Countercurrent multiplier

water moves from the filtrate to the blood due to opposite direction movement

kidney function

driven by the overall fluid balance in your body

Fluids outside of your cells

fluids in plasma and spaces between cells in blood and lymph

Dehydration

ICF goes down, fluids from ECF will compensate and move from ECF to ICF to hydrate cells

Volume change of ECF

signal for kidneys to reabsorb more fluids or more water