II: 9 - Excretion in humans Flashcards
Lots of stuff about the kidney
Define
excretion
The removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements, including carbon dioxide, urea, spent hormones and salts.
The organs of excretion in humans include the skin, lungs and kidneys.
What is the role of the liver in excretion?
- forms urea from excess amino acids by deamination
- site of breakdown for alcohol, drugs and hormones
What is the function of the kidney?
Removal of urea and excess water and the re-absorption of glucose and some salts
Name blood vessels A and C
A: aorta
C: inferior vena cava
State the names of blood vessels B and D.
What is in the blood they carry?
B: renal vein
- deoxygenated blood
- no metabolic waste
- little nutrients
D: renal artery
- oxygenated blood
- metabolic waste
- nutrients
Name structures E, F, G and H, and state their functions
- Kidney: carries out excretion
- Ureter: transports urine from kidney to bladder
- Bladder: stores urine before it is expelled from the body, has sphincter muscle to hold urine in
- Urethra: transports urine from bladder out of the body
State the name and function of A
Cortex
Contains nephrons that filter the blood
State the name and function of B
Medulla
The middle layer containing loops of Henle and colleting ducts
State the name and function of C
Pyramids
Contains tubules/collecting ducts that transport urine from nephrons to pelvis
State the name and function of D
Fribrous renal capsule
Composed of tough fibres protecting the kidney
State the names of structures E, F and G
E: ureter
F: renal vein
G: renal artery
State the name and function of H
Renal pelvis
Area where all collecting ducts come together and connect with the ureter
State the name and function of A
Afferent arteriole (branch of renal artery)
Carries unfiltered blood into nephron
State the name and function of B
Glomerulus
High pressure capillary bed that plasma leaks out of, containing salts, glucose, amino acids, hormones, creatinine and nitrogenous wastes.
This process is known as ultrafiltration.
Red blood cells and plasma proteins do not leak out of the glomerulus as they are too large.
State the name and function of C
Bowman’s capsule (renal capsule)
Collects filtrate from glomerulus and leads into the renal tubule
State the name and function of D
Efferent arteriole
Has a smaller diameter/lumen than the afferent arteriole, causing high pressure in the glomerulus.
Leads to capillary network surrounding the nephron for selective reabsorption.
State the name and function of E
Near tubule / Proximal convoluted tubule (PCT)
Site for selective reabsorption, where cells lining the tubule reabsorb useful substances (e.g. glucose, amino acids, useful salts and some water) by active transport. These substances then diffuse back into the blood.
The cells have lots of mitochondria for respiration to provide ATP energy for active transport.
State the name and function of F
Loop of Henle
Site of osmoregulation, where further reabsorption of water and salts occurs.
State the name and function of G
Far tubule / Distal convoluted tubule (DCT)
More wastes are added, salt and water level balanced, pH balanced
State the name and function of H
Collecting duct
Takes urine to pelvis and ureter
Define
osmoregulation
The regulation of water and salt level in the body to to maintain the homeostasis of the organism’s water content and osmotic pressure
Describe what happens in osmoregulation when there is too litter water
- Hypothalamus senses too little water
- Hypothalamus sends message to pituatary gland to produce ADH (anti-diuretic hormone)
- ADH travels in the blood to kidney
- Tubule walls become more permeable (loop of Henle)
- More water is reabsorbed
Describe what happens in osmoregulation when there is too much water in the body
- Hypothalamus senses too much water
- Hypothalamus sends message to pituatary gland to produce less ADH
- Kidney receives less ADH via the bloodstream
- Tubule walls are less permeable, so less water is reabsorbed
Describe how dialysis works
- Blood is pumped from an artery into the dialyser through a tube. A roller pump maintains pressre and rate of flow of blood, and an anticoagulant is added to prevent clotting.
- Dialysate (solution in dialyser) has solute concentrations identical to normal plasma, and no wastes.
- Blood flows through semi-permeable membrane.
- wastes diffuse out (moves down the concentration gradient)
- useful substances either diffuse in or out to reach the correct concentrations
- red blood cells and plasma proteins are too large to diffuse out
- Blood flows out, through a bubble trap and filter, and into the patient’s vein.
List the advantages and disadvantages of dialysis
Advantages:
- Widely available (unlike kidney transplant)
- No ethical/religious conflicts
- Easier; doesn’t require medication
- None of the risks of transplants
Disadvantages:
- Time consuming and tiring
- Patients must strictly regulate diet and fluids
- Expensive over time
List the advantages and disadvantages of kidney transplants
Advantages:
- No need for regular dialysis treatment
- Improved quality of life
Disadvantages:
- Long wait on the transplant list
- May conflict with ethical/religious beliefs
- Tissue rejection possible
- Immunosuppressants required to reduce risk of rejection; these weaken the immune system
- Expensive in the short term
- Risks during surgery, e.g. infection
