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3.7 Homeostasis and the Kidney, image - Coggle Diagram
3.7 Homeostasis and the Kidney
Homeostasis = the process of maintaining the body in a state of dynamic equilibrium (constant internal state despite changes in the external environment)
A normal 'set point' is maintained through negative or positive feedback when a change occurs.
Positive feedback is used to enhance a stimulus size
Negative feedback uses detectors/receptors, a control centre/coordinator and a response
Urinary System
It has two main functions - osmoregulation and removal of urea
Key points to remember:
high levels of urea are present in oxygenated blood which is flowing from the heart to the kidneys
there are lower levels of urea present in deoxygenated blood which flows back to the heart
Kidney Structure
The outer region of the kidney is called the cortex - this is where renal arteries eventually become nephrons therefore where ultrafiltration occurs
The central region of the kidney is called the medulla - this is where osmoregulation occurs
The origin of the ureter is called the renal pelvis - this is where urine is formed and passed on.
Nephron Structure
The part of the nephron in the
cortex
contains the glomerulus, proximal convoluted tubule and distal convoluted tubule.
The part of the nephron in the
outer medulla
contains the thick regions of descending and ascending limbs of the loop of Henle and the upper region of the collecting duct
The part of the nephron in the
inner medulla
contains the thin regions of the descending and ascending limbs of the loop of Henle
Glomerulus and Bowman's capsule
The glomerulus is surrounded by the Bowman's capsule
to get to the glomerulus the blood goes through the afferent arteriole which is wider and the efferent arteriole which is smaller this different is so that the different increase the hydrostatic pressure
There are pores between cells in the endothelium of the capillaries in the bowman's capsule - often called fenestrations or slits which are there to speed up the filtration process
Podocytes are cells of the bowman's capsule inner wall which wrap around the capillaries of the glomerulus
Gaps between podocytes allow free passage of filtrate from the blood into the renal capsule lumen
Basement membranes of capillaries and podocytes act as selective barriers which allow water and small molecules to pass into the nephron
Filtration efficiency is increased in a few different ways
Surface area is increased by the 'feet' of the podocytes aiding filtration
there is a small distance between podocytes and capillaries decreasing travel distance
between the 'feet' of the podocytes there are channels which increase the concentration between the tissue fluid
Mechanism of ultrafiltration
