excretion

Question 1

definition of excretion

Answer 1

removal of metabolic waste products and toxic substances from the body

Question 2

what is metabolism?

Answer 2

metabolism = catabolism + anabolism
* anabolism : simple molecules built up into complex molecules with intake of energy
* catabolism: complex molecules broken down into simple molcules with release of energy

Question 3

why must metabolic waste products be removed from the body?

Answer 3

• harmful if accumulates in body

Question 4

egestion vs excretion

Answer 4

• egestion: removal of undigested matter not produced by metabolism
• excretion: removal of metabolic waste products

Question 4

how do unicellular and multicellular organisms carry out excretion

Answer 4

• unicellular: by diffusion
• multicellular: by special excretory organs

Question 5

parts of urinary system

Answer 5

1. hilum
2. kidney
3. ureter
4. bladder
5. sphincter muscle
6. urethra

Question 6

what is the hilum

Answer 6

depression where renal artery, renal vein and nerves are connected to kidney

Question 7

what is the kidney

Answer 7

• bean-shaped organ
• removes nitrogenous waste products, excess mineral salts and excess water
• regulates salt and water balance in blood plasma
• mantains pH and composition of blood plasma

Question 8

what is the ureter

Answer 8

• narrow tube that emerges from hilum
• brings urine from kidney to bladder

Question 9

what is the bladder

Answer 9

elastic, muscular bag that stores urine

Question 10

what is the sphincter muscle

Answer 10

• found at bottom of bladder
• controls urine flow

Question 11

what is the urethra!!!!!

Answer 11

duct which urine passes from bladder to outside the body

Question 12

what do renal arteries vs renal veins do

Answer 12

1. renal arteries - bring oxygenated blood containing nitrogenous waste products, mineral salts and excess water from heart to kidney
2. renal veins - bring deoxygenated blood (no nitrogenous waste products, mineral salts or excess water) from kidney to heart

Question 13

what are the 2 regions of the kidney

Answer 13

1. cortex : outer darker red region enclosed by fibrous capsule
2. medulla: inner thicker paler red region, contains pyramids

Question 14

structure of a nephron

Answer 14

• basic functional unit of kidney
• each kidney has 1 million nephrons
• tiny tubules where urine is formed
• open into the collecting duct (tube)

Question 15

4 main parts of a nephron

Answer 15

• Bowman’s capsule
• proximal convoluted tubule
• Loop of Henle
• distal convoluted tubule

Question 16

urine is formed through which processes

Answer 16

1. ultrafiltration
2. selective reabsorbtion

Question 17

what happens in ultrafiltration

Answer 17

• occurs in glomerulus (renal artery splits into arterioles, which further split into capillaries called glomerulus)
• removes small molecules from the glomerular blood capillaries into the bowman’s capsule to form the glomerular filtrate
• FILTERED OFF: water, glucose, amino acids, nitrogenous waste products (urea) , mineral salts (SMALL MOLECULES)
• NOT FILTERED OFF: blood cells, platelets, proteins, fats (LARGE MOLECULES)

Question 18

2 conditions for ultrafiltration to occur

Answer 18

1. high hydrostatic blood pressure in glomerulus due to wide afferent arteriole and narrow efferent arteriole (MAIN force of ultrafiltration)
2. glomerulus walls are partially permeable with small pores so water and small molecules can pass through

Question 19

what happens during selective reabsorbption

Answer 19

• useful substances (glucose, mineral salts, water and amino acids) are reabsorbed from the glomerular filtrate
• occurs through proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct into blood capillaries
• excess water, excess mineral salts and nitrogenous waste products (urea) pass out of the collecting duct as urine

Question 20

what is reabsorbed at proximal convoluted tubule

Answer 20

1) by active transport & diffusion:
* all glucose
* all amino acids
* most mineral salts

2) by osmosis:
* most water

Question 21

what is reabsorbed at loop of henle, distal convoluted tubule and collecting duct

Answer 21

• loop of Henle: some water (osmosis)
• distal convoluted tubule: some mineral salts (active transport & diffusion)
  some water (osmosis)
• collecting duct: some water (osmosis)

Question 22

causes of kidney failure

Answer 22

HI DI AL DA CO
1. high blood presure
2. diabetes
3. alchohol abuse
4. damage to kidneys
5. complications due to surgery

Question 23

ways to treat kidney failure

Answer 23

1. kidney transplant
2. haemodialysis
3. peritoneal dialysis

Question 24

what happens during haemodialysis

Answer 24

1. **blood** is channelled from a **vein** to a **dialyser tubing** of **dialysis machine** 2. **tubing with partially permeable walls is bathed** in a **specially controlled dialysis fluid** 3. **small molecules of metabolic waste products diffuse out of the tubing into the dialysis fluid**. **large molecules remain in the tubing** 4. **filtered blood** is **return to the person's vein in their arm**

Question 25

features of dialysis machine

Answer 25

1. **TUBING OF DIALYSER IS LONG, NARROW AND COILED** → **increase surface area to volume ratio** to **speed up exchange of substances** 2. **DIALYSIS FLUID HAS NO METABOLIC WASTE PRODUCTS** → **steep concentration gradient** for **metabolic waste products** to **diffuse out of the tubing into dialysis fluid** 3. **DIALYSIS FLUID HAS THE SAME CONCENTRATION OF ESSENTIAL NUTRIENTS** → ensure **nutrients do not diffuse out of blood** 4. **DIRECTION OF BLOOD FLOW IN TUBING IS OPPOSITE OF THE FLOW OF DIALYSIS FLUID** → **mantains concentration gradient** between **blood and dialysis fluid** for **removal of metabolic waste products**