Excretion

Question 1

Q1: What is excretion?
Q2: Human excretory products?
Q3: What organs remove these products?

Answer 1

Q1: The removal of toxic materials and metabolic waste products from organisms
Q2: urea, uric acid, carbon-dioxide, excess water and salts, bile pigments, hormones.
Q3: Lungs: CO2 and water
Kidneys: nitrogenous waste (urea etc), excess water, salts, hormones, drugs
Liver: bilirubin (breakdown of haemoglobin) done by liver, expelled with faeces
Skin: water and some urea (though sweat is a temperature regulation response)

Question 2

Kidneys
Q1: What are kidneys, what is their location and function?
Q2: Structures in the kidney?
Q3: Structure of nephron?

Answer 2

Q1: Bean shaped red-brown structures enclosed in a transparent membrane
- attached to the back of the abdominal cavity
- Removing urea and excess salts and water from the blood
Q2: Consists of many tubules called renal tubules.
- dark outer region called cortex, lighter inner region called medulla
- the place where ureters join the kidney: renal pelvis.
Q3: A nephron is a single glomerulus with its renal capsule, tubule and blood capillaries
- Renal artery divides up into many capillaries and arterioles in the cortex
- Each arteriole leads to a glomerulus (a repeatedly divided capillary, forming a knot of vessels)
- Each glomerulus is surrounded by renal capsule (cup chapped organ)
- Renal capsule leads to a renal tubule
- This tubule has a series of coils and loops
- It then joins a collecting duct, which passes through the medulla and opens into the pelvis (ureter)
- There are thousands of glomeruli in the kidney cortex

Question 3

Q4: How exactly do kidneys perform their function?

Answer 3

Q4: Ultrafiltration: High blood pressure in glomerulus causes part of the blood plasma (salts, glucose, urea, uric acid) to leak through the capillary walls. (RBCs and plasma proteins don't)
The filtrate (salts, glucose, urea, uric acid) collects in the renal capsule, and trickles down the renal tubule.
Selective Reabsorption: The capillaries which surround the tubule absorb the substances needed by the body back into the blood (all the glucose, much of the water, some of the salts).
The things not needed (some water, salts, urea) continue down the renal tube into the pelvis of the kidney. Form urine and pass down the ureter into the bladder.
Urine leaves the body through the urethra.

Question 4

Kidney Dialysis
Q1: What is dialysis?
Q2:  What becomes the first cause of death when someone’s kidneys fail?
Q3: What is a dialysis machine?
Q4: How is dialysis carried out?

Answer 4

Q1: Filtering of blood by diffusion of waste products and salts through a membrane
Q2: Potassium imbalance in the blood, which causes the heart to fail.
Q3: A long cellulose tube with submicroscopic pores coiled up in a water bath, containing the correct concentrations of salts and glucose, and of waste products
Q4: The patient’s blood is led from a vein in the arm and pumped through the cellulose tubing.
Blood is pumped in the opposite direction to the flow of water in machine (to maintain a concentration gradient)
The concentration, acidity and temperature of the fluid are constantly adjusted.