Topic 1 - Homeostasis And The Kidney Flashcards
What is excretion
The removal from the body of toxic waste products of metabolic processes
How and where is Carbon Dioxide excreted from the body in mammals
Carbon dioxide is excreted during respiration from the lungs
What is homeostasis
The maintenance of steady states within the body
What are the main properties in the kidney
An outer cortex
An inner medulla
The pelvis
Nephrons
Connecting Ureter
What are the distinct regions in the nephron
A cup-shaped Bowmans capsule
The Proximal Convoluted Tubule
The Loop of Henle
The Distal Convoluted Tubule
The Afferent Arteriole
The Glomerulus
The Efferent Arteriole
The Collecting Duct
What is ultrafiltration
The stage in which plasma in the glomerulus is filtered into Bowmans Capsule. Only substances below a certain size are filtered and so the filtrate contains useful molecules as well as toxic ones
Why is the blood entering the glomerulus under high hydrostatic pressure
The renal arteries are wide, short and relatively close to the heart
The efferent Arteriole is smaller than the afferent Arteriole which creates a bottleneck
Why is Ultrafiltration so efficient
15-20% of the water and solutes are removed from the plasma that flows through the glomeruli
What are the 3 layers separating plasma from filtrate
The capillary endothelium, the basement membrane on which the capillary cells lie, and the inner layer of the Bowman’s capsule
What are the porous layers of the plasma and filtrate, and why
The endothelium of the capillaries in the glomerulus, which consists of a single layer of squamous cells with pores between them
The inner wall of the Bowmans capsule consists of Podocytes, with foot like processes which surround the capillaries but which have spacious gaps between them
What is the effective filter, and where is it located
Basement membrane, this lies on the outer side of the capillary endothelium
What cells can pass through the basement membrane
Molecules with a relative molecular mass of less than 68,000
What are the constituents of blood after the filtering of the basement membrane
Inorganic ions
Glucose
Amino acids
Urea
Other toxic molecules
How is water, ions, glucose and amino acids, and small proteins reabsorbed in the PCT
Water by osmosis
Ions partly by diffusion and partly active transport
Glucose and amino acids by active transport
Small proteins by Pinocytosis
What is the composition of a proximal tubule cell
Cuboidal epithelial cells, which line the tubule walls, which have numerous microvilli on the luminal surface and infoldings of the basal cell-surface membrane next to the blood capillaries. The cells have many mitochondria located near the infoldings
What ions pass out of the ascending limb in the Loop of Henle
Sodium and Chloride
How is an osmotic gradient created in the loop of Henle
Sodium and chloride pass out of the ascending limb into the surrounding tissue of the medulla
What does an osmotic gradient in the Loop of Henle cause
It draws water out of the permeable descending limb, to be carried away by blood in the surrounding capillaries
Is water saltier as it goes up or down the Loop of Henle
Going down the descending limb
How does reabsorption in the DCT occur
The ionic composition and the pH of the blood are adjusted. Depending on the permeability of the tubule walls, some water maybe be reabsorbed
What is the function of Antidiuretic hormone
It increases the permeability to water of the walls of the second convoluted tubule and collecting duct
Where is ADH produced, and where is it secreted
It is produced by the hypothalamus, but secreted into the posterior lobe of the pituitary body
What is the function of Osmoreceptors
To detect a rise and decline of blood concentration in the Kidney. They then send impulse to the posterior lobe of the pituitary gland
How is a more concentrated (hypertonic) urine produced
The lobe of the pituitary gland releases more ADH into the blood which increases the permeability to water of the second convoluted tubule and collecting duct. Water moves through aquaporions which open, under ADH, to let water through
How is a less concentrated (hypotonic) urine produced
A fall in blood concentration inhibits the release of ADH. As a result, the walls of the second convoluted tubule and collecting duct become impermeable to water, meaning less water is reabsorbed
What is feedback in Osmoregulation
Since a change in the water potential of the blood will ultimately lead to another change in the water potential of the blood
What is negative feedback in Osmoregulation
Since an increase in water potential will later result in a decrease in water potential
How do the Kidneys excrete nitrogen-containing compounds
During the breakdown of excess amino acids and nucleic acids in the liver
What is the nephron
The functional unit of the Kidney
What constituents of blood cannot pass through the basement membrane
Plasma proteins
Where does Arteriol blood enter and go to in the Urinary system
Arteriol blood enters each capsule through an afferent arteriole which branches to form a capillary network called the glomerulus, which leads to the efferent arteriole
What are the 3 basic homeostatic response features
A control system with sensors
The correct mechanism to bring the changes back to a normal level
A negative feedback system
What is Osmoregulation
The control of the water potential of body fluids
What is reabsorption
The selective absorption of useful products back into the bloodstream from the nephron
