Lectures 8-10 Flashcards
(168 cards)
1
Q
Where is the liver in the body?
A
Just below the diaphragm
2
Q
How heavy is the liver?
A
1-1.5kg in healthy individuals
3
Q
What are the two major vessels that supply the liver?
A
The hepatic artery (around 20%)
The hepatic portal vein
4
Q
Blood leaves the liver via what?
A
A number of hepatic veins
5
Q
How big is the hepatic portal vein?
A
Around 7-8cm
6
Q
What does the hepatic portal vein carry?
A
Substances absorbed from the intestinal tract into the blood via the vein
Carries water soluble substrates arising from the diet (monosaccharides and amino acids)
7
Q
What do lymph vessels carry?
A
Products of fat digestion
8
Q
What are hepatocytes?
A
Liver cells which make up the majority of the liver volume (80%)
9
Q
What other cells apart from hepatocytes are in the liver?
A
Endothelial cells and macrophages
10
Q
What do hepatocytes appear as?
A
Hexagonal units (lobules) 1mm across
11
Q
At each corner of the hepatocyte (lobule) there is a triad of 3 vessels, what are they?
A
Tiny branches of the portal vein, hepatic artery and the bile duct
12
Q
How does blood flow between hepatocytes?
A
Via sinusoids (like capillaries)
13
Q
What is metabolic zonation?
A
The different cells in the liver have different functions
14
Q
What are the main functions of the liver?
A
Main organ of metabolism and energy
Metabolism: concerting food into energy
Energy storage
(Other functions): bile production, storage of iron and vitamins, detoxification
15
Q
What is a monosaccharide?
A
A basic carbohydrate unit
16
Q
What are the most common monosaccharides?
A
Pentose (5 carbon atoms)
Hexoses (6 carbon atoms)
17
Q
Monosaccharides join up to form chains, such as?
A
Disaccharides (2 units)
Polysaccharides (>10 units)
18
Q
Glucose and monosaccharides circulate freely in blood but what facilitated their entry into cells?
A
Specific carrier proteins
Eg liver cells have GLUT-2 glucose transporter predominantly
19
Q
What is glycogen?
A
A branched polysaccharide
Stored in cells as granules
Highly hydrated
20
Q
Why does glycogen branch?
A
It creates more ends for enzymes to operate on
21
Q
Saturated fats = ?
Mono-unsaturated fats = ?
Poly-unsaturated fats = ? Yeah
A
No double bonds
One double bond
Several double bonds
22
Q
How are fatty acids transported and why are they transported like this?
A
In the plasma bound to the protein albumin.
As they have long hydrophobic tails which are insoluble in water
23
Q
What is the purpose of fatty acids?
A
The form in which lipid energy is transported around the body
24
Q
What is triacylglycerol?
A
3 individual fatty acids and a glycerol
It is the most abundant lipid in the water
Hydrophobic (so carried in plasma as lipoproteins)
Main way fat is stored in the body
25
What are proteins?
Chains of amino acids (20 different types of amino acids)
9 essential in diet (body cannot manufacture)
Water soluble
Can be used as an energy store
26
Which hormones have a big effect on the live?
Insulin and glycogen are released into the hepatic portal vein and so have a big effect on the liver
27
What cells within the pancreases secret glucagon and insulin?
Islets of Langerhans
A-cells = glucagon
B-cells = insulin
28
When glucose concentration rises above 5 mmol/L what is released?
Insulin
29
Purpose of glucagon
To elevate blood glucose
It is suppressed when glucose concentration is high
Glucagon has no important metabolic effect in any tissue other than the liver
30
Purpose of cortisol
Released from the adrenal glands
Strong influence on metabolic pathways which take part in the liver
It stimulates gluconeogenesis
31
Purpose of adrenaline (epinephrine)
Released from adrenal glands
Effects the liver
The net effect of a rise in adrenaline leads to a breakdown of stored fuels triacylglycerol and glycogen
32
What is a normal blood glucose level?
5mmol/L
33
Brain requires stable glucose levels for fuel, below what mark is dangerous?
3mmol/L
34
What are the 3 major ways glucose enters the bloodstream?
Absorption from the intestines
Breakdown of glycogen in the liver
Gluconeogenesis in the liver
35
What is gluconeogenesis
The synthesis of carbs from other precursors
36
What is glycogenolysis
Liberate carbs, stored in the liver after meals, into the bloodstream
37
Facts about gluconeogenesis
Mainly occurs in the liver
Occurs during periods of: starvation, low-carb diets
3 main substrates for gluconeogenesis are: lactate, glycerol and amino acids
The purpose it to maintain steady blood glucose for the brain
38
Go over diagrams with recap
Around pages 22/23
39
What is de novo lipogenesis
Synthesis of fatty acids from non-lipid precursors (where fatty acids are made)
A pathway for disposing of excess carbohydrates
Leads to liver fat storage and metabolic diseases where there is a high energy diet (because it stores carbs into fats)
40
In terms of protein metabolism what is the liver the only organ capable of doing
Eliminating nitrogen from amino acids
41
What does amino acid oxidation provide for the liver?
About half the livers energy requirements
42
After an individual has their breakfast what happens in the hours after in their liver?
The liver switches from production to storage and utilisation of glucose
43
After an individual has their lunch what happens to their liver in the hours after?
The events that occur at breakfast occur but to a greater extent
Eventually de novo lipogenesis will occur
44
Basic understanding of what the liver does
Releases stored energy at times of high metabolic demand
And
Replenishes energy stores during nutrient excess
45
What happens in terms of the liver when we exercise?
Increase liver glucose output, mainly from glycogenolysis, but also gluconeogenesis
Increase in adipose tissue lipolysis and FFA mobilisation
46
Look at slides with recap
Slides 38 and 39
47
During exercise what can the liver do with amino acids to turn them into a more useful fuel source for the muscle
They can be recycled in the liver to make glucose
48
What happens to the associated nitrogen that is produced when the liver turns amino acids into glucose?
It is excreted via urea in the kidneys
49
What happens to liver metabolism during exercise?
It is not dominant because of reduced blood flow
50
Slide 42 with recap
Diagram one
51
Name some adaptations the liver undergoes after exercise training
More effective at utilising fat for fuel
| Reduced liver fat content (good for the sedentary)
52
What are the parts of the GI tract?
```
Mouth
Oesophagus
Stomach
Liver
Gall bladder
Pancreas
Small intestine
Ileum
Large intestine (colon)
Rectum
Anus
```
53
What is the name of the process that occurs where food moves down the oesophagus?
Peristalsis
54
What is in the stomach that helps break down food?
Hydrochloric acid
Enzymes
Hormones
55
What happens in the pancreas?
Enzyme production
56
What is the structure in the liver that secretes something? And what does it secrete?
The gall bladder, secretes bile
57
Is bile an enzyme?
No
58
What is the job of bile?
It is important in the emulsification of fats
59
What is an emulsifier?
Breakdown of larger fat molecules into smaller ones, providing a larger surface area for enzymes to act to digest the fats into fatty acids and glycerol
60
What does the small intestine do?
Absorb the things we’ve broken down like carbs and protein
61
What is the structure in the small intestine that allows us to absorb nutrients
Mycrovilli
62
What is the SA of the small intestine equal to?
Tennis court roughly
63
What is the main function of the large intestine (colon)?
To absorb water
64
What is there on the surface of the tongue? And what is the purpose of this?
Tastebuds, part of the reflex where if your food tastes bad or a slimy taste, triggers the spitting/vomiting reflex
65
What is the structure that prevents your food from going down the trachea?
Epiglottis
66
What does the rectum do?
Stores faeces
67
What does the GI in GI tract stand for?
Gastrointestinal
68
What is the function of the mouth and oral cavity?
To breakdown the food to mix it with saliva that contains enzymes that start to breakdown the food
69
What is another function of saliva other than enzymes to breakdown food? (X2)
Moistens the food
Protective function - contains lysosine - breakdowns bacterial cell walls to start preventing bacteria from entering the GI tract
70
You have 4 incisors at top and bottom (ones I’m worried about if they’re moving) what is the purpose of an incisor tooth?
Cutting food into pieces
Incisors are first teeth to come in
71
How many sets of canine teeth do you have on the top and bottom sets? What’s their purpose?
2
To tear meat
72
What is the purpose of molars
Grind food
73
Because older people can get damaged enamel what must you recommend for their diet
Foods that don’t hurt as much to eat, softer foods
74
How many muscles does the tongue have?
8
4 extrinsic muscles (attached to bone at the back of the mouth)
4 intrinsic muscles (not attached to bone allow you to move the tongue freely) (their job is to change the shape of the tongue)
75
Where are circumvallate papilla found? And what do they do?
The back of the tongue just in front of the tonsils
They contain your taste buds (sweet, sour, bitter, salty) (and umami)
76
What enzymes are in the salivary glands
Salivary amylase - breaks down starch
Lingual lipase - breaks down fat
77
Parotid gland produces saliva that is more what?
Watery and has enzymes in
78
The sublingual gland and submandibular gland produces what?
Saliva that is more mucus (does contain amylase and lipase and water as well)
79
What is the protein in mucus that enables it to do its job?
Mucin
80
What signals you to start producing saliva?
Sight and smell and taste of food?
Smell is the most powerful one
81
How does peristalsis work in the oesophagus?
Muscle contracts behind the food, constricting passageway and pushing food down, muscle relaxes in front of the food to minimise resistance
82
What is the purpose of the Interstitial (ICC) cells?
Only found in smooth muscle layer of GI tract
| Function is to regulate contraction of the muscles
83
The ICC cells are co-ordinated via what?
The sympathetic nervous system in order to control the passage of food
84
In a situation of fear what happens to the GI tract? And why?
It stops
| So that all the blood can get to your muscles to help with the fight or flight response
85
What’s are the layers of the GI tract?
Inner lining - mucosal layer (consists of epithelial tissue moistened by glandular secretion)
Submucosa layer - connective tissue (contains blood vessels)
Smooth muscle layers (circular layer and a longitudinal layer (they enable peristalsis))
Serosa - connective tissue that holds the structure together
86
Why do you need more mucus and lubrication towards the end of the GI tract?
As good passes down the GI tract more and more moisture is removed and so the composition of the bolus is getting more dehydrated (could lead to constipation)
87
What is a bolus?
Fancy word for food going through GI tract
88
Which part of the GI tract does not secrete enzymes
Small intestines (enzymes for this come from elsewhere)
89
What is the purpose of the stomach?
To undergo rhythmical contractions to mix food with hydrochloric acid and pepsin to break it down
90
Top of the stomach is called?
Bottom is called?
Fundus region
Pyloric region
91
What is pepsin?
An enzyme that breaks down proteins
92
What do rugae cells do?
Allow the volume of the stomach to expand to you can eat more
93
What does the pyloric sphincter do?
Controls the movement of food from the stomach into the duodenum
94
In the stomach lining there are villi, in the villi there are structures called what?
Gastric pits
95
What are gastric pits?
Indentations of the stomach wall lining (epithelial wall lining) its where you produce hormones acid and pepsinogen
96
What secretes pepsinogen?
Chief cells at the bottom of gastric pits
97
What is pepsinogen?
An inactive form of pepsin (an inactive form of an enzyme is secreted because if it was the active form it would start acting on the cells before it had even got to the food, damaging the cell lining)
98
What do G cells produce? And where do they secrete them into?
A range of hormones (eg gastrin)
They are secreted into the blood supply for the stomach (so that they act on other epithelial cells in order to signal the production of more hydrochloric acid in order to active pepsinogen
99
What do parietal cells produce?
They secrete intrinsic factor
(Essential for the absorption of vit B12)
Without intrinsic factor you won’t absorb B12 from the small intestine which can help with respiration and energy metabolism
100
How does hydrochloric acid act on pepsinogen?
Turns it into the active pepsin
| Pepsin can actually activate itself form pepsinogen
101
What is the other main role of hydrochloric acid?
Acts as an anti infective agent
102
Adult humans do not secrete what?
Lipase
103
How does the proportion of goblet cells change as you move from the small intestine to the large intestine? And why?
It increases, to increase the amount of mucus that is secreted
104
Where are panet cells found? And what role do they have?
At the bottom of crypt cells
They have an anti microbial role and to further protect the epithelial layer from absorbing toxins and bacteria etc
105
What are the main enzymes for carbohydrates?
Amylase (breaks down starch glycogen and dextrin into smaller disaccharides and) (breaks these down into maltose and glucose)
The sugar maltose is broken down by the enzyme maltase, maltose is broken down in glucose and galactose
Lactose is the specific enzyme to breakdown the sugar in milk, broken down into glucose and galactose
Sucrase breaks down sucrose (the product of maltose) into glucose
106
What are the main enzymes for proteins?
Pepsin
Chimatripsin and tripsin (breakdown polypeptides into dipeptides)
Caboxy peptidase (break off individual amino acids)
Amino peptidase (break off individual amino acids)
107
Can bike be reabsorbed into the small intestine?
Yes
108
What is another job of bile?
To neutralise the acidic contents from the stomach
109
Water soluble nutrients like glucose and amino acids and water soluble vitamins pass form the villi into where
The capillaries in the centre of the villi
110
The capillaries from the centre of the villi then go where?
From the intestines direct to the liver via the hepatic portal vein
111
What is the hepatic portal vein the control for?
Water soluble nutrients
112
What does the lymphatic system control the absorption of?
Fat soluble nutrients
113
Lipids, triacylglycerides, cholesterol and phospholipids are packaged into what?
Lipoproteins
114
Do lipoproteins go directly to the liver?
No, they pass around the entire body via the lymphatic system first, so they can have their fat taken up by peripheral cells before it goes back to the liver
115
What are the three colons in the large intestine?
The ascending
The transverse
The descending
116
Main role of the large intestine
Water reabsorption
117
Where are your kidneys
At the back just above the hip bone
118
What does the kidney do?
Acts as a filter for the plasma component of the blood, however most proteins do not get filtered apart from albumin
119
What is the whole point of the kidney?
To balance the ion composition of the blood
120
How does our urine get from the kidneys to the bladder?
Ureters
121
What are the two main structures within the kidney?
The cortex and medulla
122
What are the structures called that filter the ureters?
Nephrons (there are millions of nephrons within the kidney)
123
What is the anatomy of the renal system?
Two kidneys (urine formation)
Just above the kidney is the adrenal gland (important in secreting hormones that regulate kidney function)
Then the left and right ureters (take urine from the kidneys to the bladder)
Bladder (where the urine is stored)
A muscular valve at the base of the ladder that control the release of that urine
Finally taken to the urethra to be excreted from the body
124
Where does the reabsorbed blood from the kidney go?
Passes back in the renal vein and goes back up to the heart
125
Kidneys have an excellent blood supply
About 0.5% of total body weight is made up of kidneys but about 20% of cardiac output goes through them
Kidneys process plasma portion of blood by removing substances from it and in a few cases by adding substances to it
Works with cardiovascular system (and others) in an integrated manner
126
The blood flow into the kidneys is regulated by what?
Hormones
127
Renal system blood flow pathway
Aorta -> renal artery -> efferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries and vasa recta -> renal vein -> inferior vena cava
128
Facts about the nephron
Total of about 2.5 million in the 2 kidneys
Each nephron consists of 2 functional components:
- the vascular component (blood supply)
- the tubular component (contains what will eventually become urine)
The mechanisms by which kidneys perform their functions depends upon the relationship between these two components
129
What are podocytes
A special type of endothelial cells found around the glomerulus and bowmans capsule
130
What happens to calcium that is bound to proteins? And what % of calcium in the blood is bound to proteins?
50% is bound to proteins and calcium that is bound to proteins is not filtered
131
Important hormones in kidneys
Parathyroid hormone (PTH) - important in controlling water reabsorption
Angiotensin - controlling the afferent and efferent arterioles (whether they’re contracted or relaxed), determines how much blood is filtered
132
What are the three basic renal processes?
Glomerular filtration (GFR)
Tubular re-absorption
Tubular secretion
133
Glomerular filtration rate is very high
Around 180litres/day of plasma
134
How is GFR controlled?
By afferent and efferent arterioles
Sympathetic vasoconstrictor nerves
Anti diuretic hormone (controls amount of water reabsorbed)
Series of hormones know as the Renin angiotensin antiogensinigen system (RAAS) - this controls how much is filtered
As well as a unique system of upstream and downstream arterioles
Auto regulation
135
What does auto regulation do?
Maintains blood supply and so maintains GFR. Also prevents high pressure surges damaging the kidneys
136
High hydrostatic pressure at glomerular capillaries is due to what?
Short, wide afferent arteriole
137
Low hydrostatic pressure is caused by what?
A long narrow efferent arteriole
138
If you want to increase your GFR what happens?
You would ensure that you’re afferent arteriole is dilated
139
A low concentration of angiotensin does what?
Contracts the efferent arteriole, so then more plasma is being filtered
140
A high concentration of angiotensin does what?
Means the afferent arteriole contracts, so less blood is coming into the glomeluli, so less plasma is being filtered
141
What controls the reabsorption of ions from the proximal convoluted tubule and back into the peritubular capillaries that are surrounding the proximal convoluted tubule?
Oncotic pressure
142
What is oncotic pressure?
The pressure due to the higher concentration of proteins within the peritubular capillaries (which has lots of proteins in) compared to the filtrate (which has no proteins in)
143
Structure of proximal tubules
Extensive brush border on surface
Re-absorption is rapid
Glucose and chlorine are co-transported coupled with sodium transport down the electrochemical gradient for sodium, requires energy
144
General rule in kidney about sodium and water
Wherever sodium goes, water follows
145
Rewatch recap at 40 minutes left
Fucking hard
146
Lots of transport proteins have what? And what does this mean?
A limited number of binding sites, once all of the binding sites are occupied you cannot have any more glucose binding. This means whatever else is left passes down into the loop of Henley
147
How is sodium absorbed back into the bloodstream?
Via active transport mechanisms
Nutrient transporters such as glucose and amino acids
Specialised sodium channels that only carry sodium called ENAC channels, occurs down the concentration gradient
148
What is the proximal tubule very permeable to?
Sodium, so ions flow down gradient across membranes
149
The electrical gradient caused by sodium moving across the proximal tubule also draws what across?
Chlorine
150
What has the fluid in the convoluted tubule had removed?
Majority of its sodium, chloride, glucose and amino acids
Meaning fluid is more concerted than what it was
151
Where does potassium reabsorption take place?
The loop of Henley
152
What happens due to the countercurrent exchange?
Potassium ions leave the loop of Henley at the deepest part
153
Where does the majority of potassium reabsorption occur?
The deepest (lowest) part of the loop of Henley
154
What % of sodium ions are reabsorbed?
99%
155
If you have a high potassium diet, what happens to the majority of the potassium? And why?
It is excreted in the loop of henley
There is a very tight homeostatic control over the amount of potassium in the body
156
What is the main function of the loop of Henley and the collecting duct is?
Is the reabsorption of water and sodium ions
| How you control the concentration of your urine
157
Where do sodium ions move out of? And where are they reabsorbed?
The ascending loop of Henley via ENAC channels
The descending loop of Henley
158
Why is this cyclical movement of sodium important?
For water re-absorption
159
Where does water re-absorption occur? In the kidneys
At the most distal part of the medulla
160
Sodium recycling only goes on where in the kidneys?
The medulla
161
What controls the active reabsorption of sodium in the distal convoluted tubule
Anti diuretic hormone
162
What else does anti diuretic hormone control?
The reabsorption of water
163
How does ADH control the reabsorption of water?
By deciding how many ENAC channels are open in the epithelial cells of the distal convoluted tubule
164
What happens when ADH binds to its receptor? And how can this affect the concentration of urine?
It causes these aquaporin channels to move to the aclical membrane, so you have more aquaporin channels in the aclical membrane, so you get more water being transported
More dilute urine = more ADH opens more aquaporin channels
165
What does the macular denser do?
Recognised when you have a low concentration of sodium ions in the tubule
166
What is the difference between the efferent and afferent arterioles?
Afferent arteriole brings blood to the glomerulus
Efferent arteriole takes blood away from the glomerulus
167
What does the renal proximal tubule contain?
The proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
168
What is the function of the proximal convoluted tubule?
Regulates the pH of the filtrate by exchanging hydrogen ions for bicarbonate ions in the filtrate
Secretes organic acids such as creatine into the filtrate
