Topic 3 - Organ Systems Flashcards
What is a fossil?
Any trace of an animal or plant that lived long ago
What are the three ways fossils can be formed?
- Gradual replacement by minerals
- Casts and impressions
- Preservation in places where no decay happens
How do fossils form by gradual replacement of minerals?
- Things like teeth, shells, bones, don’t decay easily so last a long time when buried
- Eventually replaced my minerals
- Form rock like substances shaped like original hard part
- Fossil stays distinct inside rock, eventually dug up
How do fossils form from casts and impressions?
- Form when organism is buried in soft material like clay
- Clay hardens around it when it decays, leaving cast of itself
- Footprints can be pressed into these materials when soft, leaving impression when hardens
How do fossils form from preservation in places where no decay happens?
-Where conditions aren’t suitable for microbes to work (e.g. glaciers, too cold; peat bogs, too acidic; amber, no oxygen or moisture)
What can we tell from fossils found in rock layers?
- What the creatures/plants looked like
- How long ago they existed (deeper rock = older fossil)
- How they’ve evolved (study similarities/differences between fossils in differently aged rocks, see how species changed/developed over billions of years)
What is the problem with the fossil record?
It is incomplete
Why is the fossil record incomplete?
- Very few dead plants/animals turn into fossils; most just decay away
- Some body parts (e.g. soft tissue) decay away completely
- Some fossils yet to be discovered
What is a pentadactyl limb?
A limb with 5 digits
What species can you see the pentadactyl limb in?
- Mammals
- Reptiles
- Amphibians
What can be the difference between the pentadactyl limb between species?
Similar bone structure but used for different functions e.g. bat vs human
What does the similarity in bone structure (pentadactyl limb) show us?
Provides evidence species with pentadactyl limb have evolved from common ancestor (that had pentadactyl limb)
What are the 3 ways you can measure the growth of an organism?
- Size (measure height, length, width, circumference)
- Wet mass (organisms contain lots of water; mass of organism depends on how much water gained/lost; wet mass is mass including all water in its body so can vary from one day to next)
- Dry mass (mass of organism with no water in body; doesn’t vary like wet mass; can only measure when organism dead; organism dried out by leaving in hot oven overnight)
What are the three processes involved in growth/development of an organism?
- Cell differentiation
- Cell division
- Cell elongation
How does an organism grow/develop by cell differentiation?
The process by which a cell changed to become specialised for its job
How does an organism grow/develop by cell division?
Mitosis
How does an organism grow/develop by cell elongation?
Where a plant cell expand, making cell bigger so making plant grow. Only happens in plants.
How does growth occur in animals?
- Cell division
- Grow when young, reach full growth + stop growing
- Cells divide fast when young
- Older: cell division only for repair (replace old/damaged cells)
- In most animals, cell differentiation lost at early age
How does growth occur in plants?
- Often grow continuously
- Continue to differentiate to form new parts
- Growth in height mainly due to cell elongation
- Cell division: usually done in tops of roots + shoots
What is a growth chart used for?
To assess a child’s growth over time, so that an overall pattern in development can be seen + any problems highlighted
Give one example of when a growth chart might be used.
After birth a baby’s growth is regularly monitored to ensure it’s growing properly
What 3 measurements of a baby are usually taken to ensure a baby is growing properly?
- Length
- Mass
- Circumference
How does a growth chart show the information?
- As a number of percentiles
- e.g. 50th percentile = mass 50% of babies reached at certain age
On a growth chart, what would cause the doctors to become concerned?
- Above 98th percentile or below 2nd percentile
- An inconsistent pattern
What are tissues?
- e.g. muscle tissue
- A group of similar cells that work together to carry out a particular function
What are organs?
- e.g. the heart
- A group of different tissues that work together to perform a particular function
What are organ systems?
- e.g. circulatory system
- A group of organs working together to form a particular function
What are the four main chambers of the heart?
- Right atrium
- Right ventricle
- Left atrium
- Left ventricle
What are the four main blood vessels of the heart?
- Pulmonary artery
- Vena cava
- Aorta
- Pulmonary vein
How does deoxygenated blood travel around the heart?
Vena cava –> right atrium –> right ventricle –> pulmonary artery
How does oxygenated blood travel around the heart?
Pulmonary vein –> left atrium –> left ventricle –> aorta
What is the role of the vena cava?
Take deoxygenated blood from the body to the heart (right atrium)
What is the role of the pulmonary artery?
Take the deoxygenated blood from the heart (right ventricle) to the lungs to become oxygenated
What is the role of the right ventricle?
Pump deoxygenated blood to the lungs to be oxygenated through the pulmonary artery
What is the role of the pulmonary vein?
Take oxygenated blood from the lungs to the heart (left atrium)
What is the role of the left ventricle?
Pump the oxygenated blood from the heart around the body via the aorta
What is the role of the aorta?
Take the oxygenated blood from the heart around the body
Why is the wall of the left ventricle more muscular than the right wall?
The right ventricle has to pump blood all around the body whereas the right ventricle only pumps blood to the lungs
What is the role of the valves in the heart?
Prevent backflow of blood
What is the role of the red blood cells?
Carry oxygen from the lungs to all the cells in the body
What is the shape of the red blood cells and how does this help them perform their function?
- Doughnut shape (bioconcave disc shape)
- Gives a large surface area for absorbing oxygen
Where is haemoglobin found and what does it do?
- Substance found in red blood cells
- Contains lots of iron
- In lungs: combines with oxygen, becoming oxyhaemoglobin
- In body tissues: reverse happens to release oxygen to cells
What don’t red blood cells have and why?
- Nucleus
- Make more room for haemoglobin
What can happen if you have a lack of iron?
A type of anaemia where blood can’t carry enough oxygen
What do white blood cells do?
Defend against disease
How do white blood cells fight against disease?
- Change shape to ‘gobble up’ unwanted microorganisms
- Produce antibodies to fight microorganisms
- Produce antitoxins to neutralise any toxins produced by the microorganisms
What can happen if you have a low white blood cell count?
Increase risk of infection
What could it mean if you have a high white blood cell count?
You have an infection or even leukaemia (cancer of the blood)
What are platelets and what do they do?
- Small fragments of cells
- Help blood to clot at a wound (to stop blood pouring out + microorganisms getting in)
What can happen if you have a lack of platelets?
Excessive bleeding + bruising
What is the role of the plasma?
- Pale yellow liquid
- Keeps the blood fluid
- Transports things around the body
What does the plasma transport around the body?
- Red/white blood cells + platelets
- Nutrients e.g. glucose + amino acids (absorbed from gut + taken to body cells)
- CO2 (waste product formed in cells; transported in blood to lungs where removed)
- Urea (waste product formed in liver; blood transports to kidneys where its removed)
- Hormones (transported from glands to target organs)
- Antibodies + antitoxins produced by white blood cells
What are the three types of blood vessels?
- Arteries
- Capillaries
- Veins
What does an artery do?
Carry blood away from the heart
What does a capillary do?
Involved in the exchange of materials with the tissues
What does a vein do?
Carry blood to the heart
What is the structure of an artery and how does this help it do its function?
- Walls thick compared to size of hole down middle (lumen)
- Contain thick layers of muscle making them strong
- Walls are strong + elastic as heart pumps blood out at high pressure
What do arteries branch into?
Capillaries
What size are capillaries?
Tiny, too small to see
How does the structure of a capillary help perform its function?
- Carry blood very close to every cell in body to exchange substances with them
- Permeable walls: so substances can diffuse in + out
- Supply food + oxygen + take away wastes e.g. CO2
- Walls usually 1 cell thick; increases rate of diffusion by decreasing distances over which it occurs
What do capillaries join up to form?
Veins
What is the structure of a vein and how does this help it do its function?
- Blood at lower pressure in veins so walls don’t need to be as thick as artery wall
- Larger lumen than arteries (help blood flow despite lower pressure)
- Have valves ti keep blood flowing in right direction
What are the big molecules that are too big to pass through the walls of the digestive system?
- Starch
- Proteins
- Fats
What are the small molecules that can easily pass through the walls of digestion?
- Sugars
- Amino acids
- Glycerol
- Fatty acids
What are the digestive enzymes and what do they break down?
- Carbohydrase (e.g. amylase): digest starch to sugars
- Proteases (e.g. pepsin): digest proteins to amino acids
- Lipase: digest fat to fatty acids + glycerol
Why are big molecules broken down into smaller molecules?
Big molecules (e.g. starch) are insoluble; broken down into smaller molecules (e.g. sugars) which are soluble
Which organ system contains food moving around the body?
Digestive system
What is the order of organs in the digestive system that FOOD PASSES THROUGH?
Mouth –> oesophagus –> stomach –> small intestine –> large intestine
What is the role of the mouth in digestion?
- Moistens food with saliva from salivary glands
- Salivary glands produce amylase enzymes in saliva that breaks down starch
- Food chewed to form ball of food (bolus) before being swallowed
What is the role of the oesophagus in digestion?
- Tube that takes food from mouth to stomach
- Lined with muscle that contract to help ball move along by peristalsis
What is the role of the stomach in digestion?
- Pummels food with its muscular wall
- Produces protease enzyme pepsin
- Produces hydrochloric acid
What is the role of the hydrochloric acid in the stomach?
- Kill bacteria
- Give the right pH for protease enzyme to work (pH 2, acidic)
What is the role of the liver in digestion?
Where bile is produced
What is the role of the bile?
- Neutralises stomach acid
- Emulsifies fat
What is the role of the gall bladder in digestion?
Where bile is stored before it’s released into small intestine
What is the role of the pancreas in digestion?
- Produces protease, amylase + lipase enzymes
- Releases these into small intestine
What is the role of the small intestine in digestion?
- Produces protease, amylase + lipase enzymes to complete digestion
- Where food is absorbed out of digestive system into body
What is the role of the large intestine in digestion?
Where excess water is absorbed from the food
Why is visking tubing a good model for a gut?
- Only lets small molecules through + not big molecules (like gut)
- Cheaper + easier than animal’s gut
Why is visking tubing not a good model for the gut?
Gut is longer + has massive surface area so speed of digestion + absorption is slightly different
What experiment can you do to model the gut?
Visking tubing filled with amylase + starch solution in distilled water
What is the colour order of Benedict’s Reagent and what does each colour show?
- blue–>green–>yello–>orange–>brick-red
- Blue when no sugar and go towards red if there is sugar presemt
When there are higher concentrations of amylase, Benedict’s Reagent gets nearer towards red; why?
- More starch being broken down into sugar
- Due to higher concentration of amylase there are more active sites available to break down starch to sugar
- So starch broken down at faster rate
- Above a certain amylase concentration reaction won’t go any faster as already enough active sites to deal with all starch
What is another name for the gut?
Alimentary canal
What are the two types of muscular tissues running down the digestive system?
- Longitudinal muscles: run down length of gut
- Circular muscles: running in circles around the gut
What are the roles of the muscular tissue running down the digestive system?
Squeeze the food along, through peristalsis
How do the circular muscles push food along the gut?
Waves of circular muscle contractions
How do the longitudinal muscles push food along the gut?
Run slightly ahead of the circular muscle contractions, as longitudinal muscle contractions, to keep food in a ball
Why is bile needed to neutralise stomach acid?
- HCl in stomach too acidic for enzymes in small intestine to work properly
- Bile is alkaline
- Neutralises acid + makes conditions alkaline
- Enzymes in small intestine work best at alkaline
How does bile emulsify fat?
- Breaks down fat into tiny droplets
- Gives larger surface area of fat for enzyme lipase to work, making digestion faster
What are the 3 features of the villi that make absorbing digested food into the bloodstream efficient?
- Big surface area: digested food absorbed more quickly into blood
- Single layer of surface cells: digested food diffuses quickly over a short distance
- Good supply via capillary network: assist quick absorption
What are probiotics?
- Live bacteria
- Good bacteria (similar to ones found naturally in gut)
Give 2 examples of probiotic.
- Bifidobacteria
- Lactobacillus (a lactic acid bacterium)
What kind of foods are probiotics added to?
-Yoghurt
-Soya milk
-Dietary supplements e.g. capsules
[-May already been there or added by manufacturer]
What benefits are probiotics thought to have?
- Keep immune system strong
- Keep digestive system healthy
What are prebiotics?
- Carbohydrates we can’t digest
- Food supply to ‘good’ bacteria already in digestive system
Which foods do prebiotics naturally occur in?
-Leeks
-Onions
-Oats
[-Not enough in normal diet for significant effect; some take supplements containing prebiotics]
What is it thought that prebiotics do?
Helps promote growth of good bacteria in gut (in turn improving digestive system’s health + immune system’s strength)
Give one example of a prebiotic.
Oligosaccharides
What are plant stanol esters?
Chemicals that can lower blood cholesterol + lower risk of heart disease
How are plant stanol esters made?
- Occur naturally in plants (in very small quantities)
- Produced commercially: use bacteria to convert sterols (types of fat found in plants like soya beans) into stanols
What foods are plant stanol esters usually found in?
- Manufacturers add to spreads + some dairy products
- Those worried about blood cholesterol may choose it over other spreads
Functional foods aren’t proven to have health benefits but claim to. What must you think to see if you think they wok?
- If reported + published scientific study in reputable journal
- Written by qualified person (not connected with sellers)
- Sample of people asked/tested large enough for reliable results
- Other studies have found similar results
