Chapter 8: Excretion in Humans Flashcards
Define excretion.
Excretion is the process of removing metabolic products, toxic substances and excess substances from the body.
Why is excretion necessary?
When metabolic waste products are accumulated in the body, it does not just cause harm; it is toxic and poisonous
Give examples of metabolic waste products.
(4 pts.)
- Carbon dioxide
- Urea
- Mineral salts
- Water
How is carbon dioxide produced?
(Excretion)
Waste product of aerobic respiration
How is carbon dioxide excreted?
Gaseous exchange in the lungs
What are the consequences if carbon dioxide is not excreted?
High blood carbon dioxide->
- Headaches
- Confusion
- Rapid breathing
How is urea produced?
(Excretion in Humans)
Excess amino acids are deaminated in the liver to form urea
How is urea excreted?
- Urine produced by the kidneys
- Sweat produced by sweat glands in the skin
What are the consequences if urea is not excreted?
High blood urea->
- Nausea
- Vomiting
How are mineral salts produced?
(Excretion in Humans)
Excess mineral salts produced in foods
How are mineral salts excreted?
- Urine produced by the kidneys
- Sweat produced by sweat glands in the skin
What are the consequences if mineral salts are not excreted?
High blood mineral salts->
- Decreases blood water potential
- Cell dehydration
How is water produced?
(Excretion in Humans)
Waste product of aerobic respiration
How is water excreted?
- Urine produced by the kidneys
- Sweat produced by sweat glands in the skin
What are the consequences if water is not excreted?
Too much water->
- Increased blood water potential
- Cells swell or burst
Is egestion considered excretion?
(Full answer, not pt.)
No. Excretion is the process of removing metabolic waste products from the body. Egestion is the removal of undigested matter that has never been absorbed into body cells and thus is not due to metabolic changes.
What makes up the human urinary system?
- A pair of kidneys
- A pair of ureters
- Urinary bladder
- Urethra
Which blood vessels carry oxygenated blood to the kidney?
(from heart)
Aorta
Renal artery
Which blood vessels carry deoxygenated blood from the kidney?
(to heart)
Vena cava
Renal vein
Which kidney is higher?
Left kidney
Describe the structure of a kidney.
- Bean-shaped
- Visible dark outer region and pale inner region
- Receives blood through renal artery
- Returns blood through renal vein
- Basic functional unit of kidney-> nephron
What are the 4 main parts that make up the structure of a nephron?
- Bowman’s capsule
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
What is the Bowman’s capsule?
The cup-like structure where each nephron begins
What is the collecting duct?
The tube that collects and drains urine formed by the nephron; urine eventually goes to the ureter
Name the parts of the nephron involved in ultrafiltration.
(incl. blood vessels)
- Afferent arteriole
- Glomerulus
- Efferent arteriole
- Bowman’s capsule
What are the two main processes to make urine?
- Ultrafiltration
- Selective reabsorption
Define ultrafiltration.
Ultrafiltration process by which small molecules are filtered out of the body by the glomerulus into the Bowman’s capsule.
Where does ultrafiltration occur?
Glomerulus
Bowman’s capsule
How does ultrafiltration occur?
- Afferent arteriole has a wider diameter than the efferent arteriole
- This creates a high blood pressure in the glomerulus
- The high blood pressure forces water and small, soluble molecules from the blood plasma out into the Bowman’s capsule (glomerular filtrate)
> e.g. water, glucose, amino acids, urea, salts, etc. - Some molecules are too large to pass through blood capillary walls of the glomerulus
> e.g. blood cells, platelets, plasma proteins, etc.
State the structure-to-function adaptations of the glomerulus.
Structure: Network of blood capillaries
How it is adapted for its function: Provides large surface area for filtration process
Structure: Walls of Bowman’s capsule and blood capillary walls are one-cell thick
How it is adapted for its function: Allows for shorter diffusion distance of small molecules or ions
Structure: Blood capillary walls have tiny pores
How it is adapted for its function: Allows small molecules or ions to pass through
Structure: Blood capillaries are covered by a thin partially permeable membrane
How it is adapted for its function: Only allows very small soluble molecules or ions to pass through, impermeable to blood cells, platelets and large molecules (e.g. protein)
Define selective reabsorption.
Selective reabsorption is the process in which useful substances that the body needs are reabsorbed into the blood capillaries
Where does selective reabsorption occur?
Proximal convoluted tubule (most)
Loop of Henle
Distal convoluted tubule
What waste substances are not reabsorbed and passed out as urine?
- Urea
- Excess water
- Excess mineral salts
What substances are absorbed during selective reabsorption?
- All glucose
- All amino acids
- Most water
- Some mineral salts
What is reabsorbed at the proximal convoluted tubule?
(+how)
- Most water (by osmosis)
- All glucose and amino acids (by active transport)
- Most mineral salts (by diffusion and active transport)
What is reabsorbed at the Loop of Henle?
(+how)
- Some water (by osmosis)
- Some mineral salts (by active transport)
What is reabsorbed at the distal convoluted tubule?
(+how)
- Some water (by osmosis)
- Some mineral salts (by active transport)
What is reabsorbed at the collecting duct?
(+how)
- Some water (by osmosis)
Define osmoregulation.
Osmoregulation is the maintenance of body water potential by controlling the water potential and solute concentration in the blood.
What is a diuretic?
A substance that promotes diuresis, the increase production of urine
Why is it important to regulate blood water potential?
(effects when b.w.p. is higher or lower)
When higher blood water potential than normal->
- (usual osmosis desc)
- Cells will swell and burst/lyse
When lower blood water potential than normal->
- (usual osmosis desc)
- Cells will shrink and crenate
Where is the antidiuretic hormone (ADH) produced and secreted?
Produced: Hypothalamus
Secreted: Pituitary gland
Describe the function of the antidiuretic hormone (ADH).
- Regulates blood water potential
- ADH acts on the cells in the walls of the distal convoluted tubule and collecting duct and makes them more permeable to water
FACTS ABOUT KIDNEY QUIZ! (answer all)
1. Shape?
2. Location?
3. Amount of blood filtered per day?
4. Amount of waste excreted per day?
5. Functions? (4 pts.)
- Shape: bean-shaped
- Location: back of abdomen, near the spine
- Amount of blood filtered per day: ~200litres
- Amount of waste excreted per day: ~2litres
- Functions:
- Filter blood
- Osmoregulator
- Facilitate RBC production
- Facilitate blood pressure regulation
What are some causes of kidney failure?
(5pts.)
- High blood pressure
- Diabetes
- Alcohol abuse (constant heavy drinking)
- Severe accidents that may physically damage the kidney
- Complications from undergoing major surgery
What are some effects of kidney failure?
- Toxic metabolic waste products accumulate
- Blood water potential cannot be regulated and cells burst/crenate
What are some solutions to kidney failure?
- Survive with one kidney
> Kidney will enlarge as it has to filter more blood - If both kidneys fail, can consider:
> Kidney transplant
> Kidney dialysis
(limit fluid, salt and protein)
How does a dialysis machine work?
(6 bullets)
- Blood is drawn from the vein and pumped through the tubing in the machine
- Blood flows over the partially permeable artificial membrane of the tubing, which is bathed in dialysis fluid
- Direction of blood flow is opposite to the flow of dialysis fluid-> maintain conc. gradient of waste products
- Small molecules (e.g. urea) diffuse down conc. gradient from the blood into the dialysis fluid.
Large molecules (e.g. proteins, blood cells,) remain in the tubing - Dialysis fluid is constantly changed.
- Filtered (/cleaned) blood is returned to the patient’s vein
What is a structure-to-functionWhat does dialysis fluid contain?
- Similar conc. of essential substances (e.g. glucose, amino acid, etc.) as healthy food
-> ensures no net loss of essential substances+ substances diffuse into the blood is there is a lack - No metabolic waste products to set up conc. gradient
-> allow waste products (e.g. urea, excess water, mineral salts, etc.) to diffuse out of blood
What is a structure-to-function adaptation of the dialysis tubing?
Structure: Long, narrow and coiled dialysis tubing
How it is adapted for its function: Increases surface area to volume ratio to increase rate of exchange of substances between patient’s blood and dialysis fluid
Differences between dialysis and normal kidney function?
PROCESS THAT REMOVES METABOLIC WASTE:
Dialysis: Diffusion
Normal kidney function: Ultrafiltration
SELECTIVE REABSORPTION:
Dialysis: No
Normal kidney function: Yes
ACTIVE TRANSPORT (across living cell membrane):
Dialysis: No
Normal kidney function: Yes
NEPHRONS:
Dialysis: No, only one continuous narrow dialysis tubing
Normal kidney function: Yes, many nephrons present
Similarities between dialysis and normal kidney function?
BOTH INVOLVE:
- Removal of metabolic waste
- Removal of excess water
- Removal of salts
