11.3 Kidney (HL) Flashcards
What is the excretory system in insects?
Malpighian tubules
How do Malpighian tubules work?
Directly branches of the intestinal tract and uptakes nitrogenous waste which is combined later with digested food and excreted via the anus
Describe the structure of the kidney
Oxygenated blood brought by the renal artery and deoxygenated removed via the renal vein
The ureter leads into the renal pelvis which branches into medulla surrounded by a cortex
What molecule in the kidney filter blood?
Nephrons
What do nephrons produce?
Urine
How will blood in the renal vein differ from that in the renal artery?
Less urea
Less water and solutes
Less glucose and O2
More CO2
Describe the components of a nephron
Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
What is the function of the Bowman’s capsule (kidney)?
First part of the nephron where blood is initially filtered to form filtrate
What is the function of the proximal convoluted tubule (kidney)?
Folded structure connected to the Bowman’s capsule where selective reabsorption occurs
What is the function of the loop of Henle (kidney)?
Selectively permeable loop that descends into the medulla and establishes a salt gradient
What is the function of the Distal convoluted tubule (kidney)?
Folded structure connected to the loop of Henle where further selective reabsorption occurs
What are the functions of nephrons?
Ultrafiltration
Selective reabsorption
Osmoregularion
Where in the nephron does ultrafiltration occur?
The glomerulus at the Bowman’s capsule
Where in the nephron does selective reabsorption happen?
In the convuluted tubules (proximal and distal)
Where in the nephron does osmoregulation happen?
In the loop of Henle a salt gradient draws water out of the collective duct
Describe the glomerulus
A knot-like capillary tuft encapsulated by the Bowman’s capsule and comprised of surface cells called podocytes
Between the podocytes and glomerulus is a basement membrane which filters blood
Describe the structure of podocytes
Cells with cellular extensions (pedicles) that wrap around the blood vessel of the glomerulus
Describe the process of blood filtration in nephrons
Blood is filtered by a mesh called the basement membrane
The glomerular blood vessels are fenestrated to allow blood to flow freely
How is the basement membrane selective?
It is size-selective
What cannot be found in the filtrate of the nephron?
Blood cells, platelets and plasma proteins
How does hydrostatic pressure aid in ultrafiltration?
Blood is forced at high pressure against the basement membrane
How is high hydrostatic pressure achieved in the glomerulus?
Wider afferent arteriole that leads into a narrow efferent arteriole
Describe selective reabsorption (kidney)
Reuptake of useful substances mostly in the proximal convoluted tubule
What feature of the proximal convoluted tubules makes it good for reabsorption?
Microvilli with tight junctions and many mitochondria
What is reabsorbed into the blood stream?
Glucose, amino acids, vitamins, hormones, (~80%) mineral ions and water
How are mineral ions reabsorbed by the proximal convoluted tubule?
Actively via protein pumps
How are vitamins reabsorbed by the proximal convoluted tubule?
Actively via carrier proteins
How are glucose and amino acids reabsorbed by the proximal convoluted tubule?
Co-transported across the apical membrane with sodium
How is water reabsorbed by the proximal convoluted tubule?
Follows the movement of mineral ions passively via osmosis
Which two key features in the kidney are involved in osmoregulation?
Loop of Henle
ADH
Where is the salt gradient in the kidney?
In the medulla in the loop of Henle (nephrons)
What is the descending limb of the loop of Henle permeable to?
Water but not salt
What is the ascending limb of the loop of Henle permeable to?
Salt but not water
How does the salt gradient change throughout the loop of Henle?
As the loop descends to the medulla it becomes more salty and hypertonic
In which way does the vasa recta blood network flow and what does this cause?
In the opposite direction to the loop of Henle which means salts released from the ascending limb are drawn down into the medulla further establishing the gradient
What effect does ADH have?
Increases water reabsorption by the kidney
How does ADH increase water absorption?
It increases the permeability of the collecting duct to water and so less water remains in the filtrate
What effect does dehydration have on blood pressure?
Decreases
What effect does overhydration have on blood pressure?
Increases
What urinary analysis could signal of disease?
Glucose (diabetes)
Proteins (may indicate disease or hormonal conditions)
Blood cells (variety of diseases including cancer)
Drugs/ toxins (PEDs)
Describe haemodialysis
Blood is removed and pumped through a dialyser which restricts the passage of certain molecules and produces fresh dialysis fluids and removes waste
What is the best treatment for long-term kidney faliure?
Kidney transplant
