5.1.2 Excretion as an example of Homeostatic Control Flashcards
1
Q
what is metabolism
A
all the chemical reactions that happen in you cells
2
Q
what are metabolic waste products
A
- substances that are not needed by cells
- e.g. CO2 and nitrogenous (nitrogen-containing) waste
3
Q
why is it important to get rid of metabolic waste products
A
- many of the products are toxic
- so if we allow them to build up in the body, will cause damage
- e.g. may affect other metabolic reactions
4
Q
what is exctretion
A
the removal of waste products of metabolism from the body
5
Q
what is CO2, and what does this mean
A
- CO2 is a waste product
- of respiration
- too much in the blood is toxic
- removed from the body by the lungs or gills
- which act as excretory organs
6
Q
what 2 things does excretion maintain
A
- normal metabolism
- homeostasis: helps to keep levels of certain substances in the blood roughly constant
7
Q
what are the 2 main functions of the liver
A
excretion and energy storage
8
Q
what biological molecule does the liver break down
A
amino acids
9
Q
where do we get amino acids from inside our body
A
eating and digesting proteins
10
Q
why does the body need to get rid of excess amino acids, and what are the 2 ways of doing this
A
- amino acids contain nitrogen in their amino group
- nitrogenous substances cannot be stored by the body
- so excess amino acids can be damaging to the body
- must be used by the body, e.g. to make proteins
- or broken down in the liver and secreted
11
Q
what is the process of the liver breaking down amino acids
A
1) the nitrogen containing amino NH2 group is removed from any excess amino acids
- this forms ammonia (NH3) and organic acids
- process is called deamination
2) the organic acids are respired to give ATP or converted to carbohydrate and stored as glycogen
3) the ammonia is too toxic for mammals to excrete directly, so combined with CO2 in the ornithine cycle to create urea [CO2 combines with NH3 in the mitochondria and forms a substance, which then enters the cycle in the cytoplasm]
4) the urea formed is released from the liver into the blood
5) the kidneys then filter the blood and remove urea as urine, which can be excreted from the body
12
Q
what other harmful substances does the liver break down, and through what process
A
- alcohol
- drugs (paracetamol)
- unwanted hormones (insulin)
- breaks them down into less harmful compounds that can be excreted from the body
- via DETOXIFICATION
13
Q
how and why does the liver break down alcohol (ethanol)
A
- is a harmful substance that can damage cells
- broken down by the liver into ethanal
- then broken down into less harmful acetic acid
- excess alcohol over a long period of time can cause cirrhosis of the liver
14
Q
what is cirrhosis
A
- disease of the liver due to alcohol overconsumption
- when the cells of the liver die
- scar tissues block blood flow
15
Q
why does the liver break down paracetamol
A
in excess in the blood, can lead to liver and kidney failure
16
Q
why does the liver break down insulin
A
- is a hormone that controls blood glucose concentration
- excess can lead to problems with blood sugar levels
17
Q
how does the liver store glycogen
A
- body needs glucose for energy
- liver converts excess glucose in the blood
- to glycogen
- stores it as granules in its cells
- until it is needed for energy
18
Q
what is a word commonly used to describe things associated with the liver
A
HEPAtic
19
Q
what are all of the veins, arteries and ducts connected to the liver
A
- hepatic artery
- hepatic vein
- hepatic portal vein
- bile duct
20
Q
what is the hepatic artery
A
- supplies the liver with oxygenated blood from the heart
- means that the liver has good supply of oxygen for respiration
- provides plenty of energy
21
Q
what is the hepatic vein
A
- takes deoxygenated blood away from the liver
22
Q
what is the hepatic portal vein
A
- brings blood from the duodenum and ileum (parts of the small intestine)
- so that it is rich with the products of digestion
- means any ingested harmful substances can be filtered out
- and broken down straight away
23
Q
what is the bile duct
A
- takes bile (product produced by the liver to emulsify fats)
- to the gall bladder to be stored
24
Q
what structures is the liver made up of
A
liver lobules
25
what are liver lobules
- cylindrical structures
- made of cells called hepatocytes
- arranged in rows radiating out from the centre
26
what is the structure of each liver lobule
- has a central vein, which connects to the hepatic vein
- has rows of hepatocytes radiating out from this centre
- also has many branches of hepatic artery, hepatic portal vein and bile duct connected to each lobule
27
how can you differentiate between the hepatic artery and the hepatic portal vein
- the hepatic artery is narrower than the portal vein
28
how is the hepatic artery and hepatic portal vein connected to the central vein
capillaries called sinusoids
29
what is the direction of blood flow in a liver lobule
- blood form the hepatic artery and portal vein travels to the central vein via sinusoids
- blood runs through these sinusoids, past the hepatocyte cells, which remove harmful substances and oxygen from the blood
- the harmful substances are broken down by the hepatocytes into less harmful substances, and these then re-enter the blood
- the blood then runs into the central vein, and all the central veins from all the lobules connect to form the hepatic vein
30
what are Kupffer cells
- also attached to the walls of the sinusoids
- remove bacteria
- and break down old red blood cells
31
what happens with bile in the liver
- hepatocytes in the liver produce bile
- they secrete it into tubes called bile canaliculi
- these tubes drain out into the bile ducts
- the bile ducts from all the lobules eventually connect up
- and leave the liver
32
how do you prepare liver tissue in order to be able to see it under a microscope
- under a light microscope
- place a sample of tissue on a microscopic slide
- and stain, so that the cells are easier to see
- can use differential staining to identify different features
- e.g. haematoxylin and eosin
33
what would you be able to see in a microscopic section of one of the liver lobules
- large white circular shape, being the central vein
- many cells radiating out from the central vein are the hepatocytes
- have a red dot in for the nucleus
- any white spaces in between these cells are the sinusoids
34
what are the 2 main functions of the kidneys
- excrete waste products, e.g. urea produced by the liver
- regulate water potential of the blood
35
what is the structure of the kidneys
- renal capsule outlining it
- outer section is the renal cortex
- the inner section is the renal medulla
- renal pyramids split up by renal columns
- join onto the renal calyx (calyces)
- which join the renal pelvis
- leading to the ureter
36
what is attached to the kidneys and the rest of the body
- the ureter goes onto join the bladder
- which ends with the urethra at the bottom
- the renal artery
- and renal vein
- also attach to the kidney
37
give an overview about how the kidneys excrete waste products through flow of blood in the kidneys
- blood enters the kidney through the renal artery
- then passes through capillaries in the cortex of the kidneys
- as it passes through the capillaries, substances are filtered out of the blood into long tubules (nephrons) that surround the capillaries
- ULTRAFILTRATION
- useful substances are then reabsorbed back into the blood from the tubules in the medulla and cortex
- SELECTIVE REABSORPTION
- the remaining unwanted substances (e.g. urea) pass along the tubules, then along the ureter to the bladder
- will be expelled as urine
- filtered blood passes out of the kidneys through the renal vein
38
what are nephrons
the long tubules along with the bundle of capillaries where the blood is filtered out in a kidney
- about one million in each kidney
39
where is the location of nephrons
- most of it is in the cortex
- but the loop of Henle and the section going to the ureter are in the medulla
40
what is the structure of a nephron
- you have the glomerulus surrounded by the Bowman's capsule
- leads to the PCT (proximal convoluted tubule) [proximal = close to the glomerulus, convoluted = so up down and wavy]
- leads to the long loop of Henle
- comes back into the distal convoluted tubule DCT
- which leads to the collecting duct
- to the ureter
- all surrounded by a network of capillaries
- made of the afferent arteriole, glomerulus, and then efferent arteriole
- follows the nephron, and then goes to the renal vein after the collecting duct
41
what does the renal artery split into in the cortex
blood from the renal artery enters smaller arterioles in the cortex
42
what is the glomerulus
- each arteriole in the cortex splits into the structure called glomerulus
- this is a bundle of capillaries looped inside a hollow ball called the Bowman's capsule
- the site of ultrafiltration
43
what is the difference between the afferent and efferent arterioles
- afferent: takes blood into each glomerulus
- efferent: takes the filtered blood away from the glomerulus
44
how is blood forced into the Bowman's capsule
- the efferent arteriole has a smaller diameter than the afferent arteriole
- means that the blood in the glomerulus is under high pressure
- high pressure forces liquid and small molecules in the blood out of the capillary
- and into the Bowman's capsule
45
what are the 3 layers that liquid and small molecules have to pass through to get to the Bowman's capsule
1) capillary wall
2) basement membrane
3) epithelium of the Bowman's capsule
46
how do the 3 layers between capillary and Bowman's capsule help filter the blood
- capillary wall has pores in the endothelium, acting as a sieve againsts larger molecules
- the basement membrane also acts as a second sieve, and prevents further molecules from entering
- the epithelium of the Bowman's capsule contains slits in it, formed by specialised podocyte cells that form the slits by wrapping extensions around the capillary, meaning any cells, platelets or large plasma proteins that may have made it past the other 2 layers don't actually enter the tubule
47
what stays in the blood even after ultrafiltration
- larger molecules like large proteins
- blood cells (red, platelets and white)
48
what do you call the liquid and small molecules that pass out of the blood in ultrafiltration, and what happens with it now
- filtrate
- now passes along the rest of the nephron
- and useful substances are reabsorbed along the way
- made of glucose, salt, urea e.g.
49
how does filtrate exit the nephron
- filtrate flows through the collecting duct
- passes out of the kidney along the ureter
50
when does selective reabsorption take place
as the filtrate flows along the PCT, through the loop of Henle, and along the DCT
51
what happens during selective reabsorption
- useful substances leave the tubules of the nephrons
- and enter the capillary network that's wrapped around them
- so are reabsorbed back into the blood
52
