Animal Tissues and Systems

Main function of the digestive system

To digest food and absorb the nutrients obtained from digestion.

Stages of digestion

1. Food chewed in mouth. Enzymes in saliva begin to digest the starch into smaller sugar molecules.

2. Food passes down oesophagus into stomach.

3. Stomach contains hydrochloric acid and enzymes like protease begin the digestion of proteins.

   Causes a churning effect with stomach muscles to increase surface area for enzymes.

4. Passed to the small intestine where enzymes from liver and pancreas are released.

   Continuing digestion of proteins and starch, whilst starting digestion of lipids. Liver releases bile which speeds up digestion of lipids, whilst neutralising acid released from stomach.

5. In the small intestine, small food molecules produced by digestion are absorbed into the bloodstream by diffusion or active transport.

6. Passed into large intestine where water is absorbed into the bloodstream and faeces are produced.

7. Faeces are released from the body.

Role of the pancreas and salivary gland

Glands which produce digestive juices containing enzymes.

Role of the stomach

Produces hydrochloric acid - which kills any bacteria present and provides the optimum acidic pH for the protease enzyme to function.

Role of the small intestine

Site where soluble food molecules are absorbed into the bloodstream.

Small intestine adaptations

• large surface area - increased absorption of products of digestion

• contains villi - increases surface area further, has very rich blood supply which increases concentration gradient, thin membrane which ensures a short diffusion pathway

Role of the liver

Produces bile which emulsifies lipids (fats) and allows the lipase enzyme to work more efficiently.

Role of the large intestine

Absorbs water from undigested food, producing faeces.

Role of enzymes in the digestive system

Act as biological catalysts which speed up the rate of biological reactions (the breakdown of food) without being used up.

Shape of an enzyme and its function

Have a specific active site which is complementary to their substrate.

Metabolism

The sum of all the reactions in a cell or an organism.

Why is the digestive system needed?

Breaking down larger molecules into smaller molecules, as bigger ones cannot be absorbed into the bloodstream.

eg. proteins broken down by proteases into amino acids

Lock and key hypothesis of enzyme function

The shape of the enzyme active site and the substrate are complementary, so can bind together to form an enzyme-substrate complex like a key to a lock.

Effect of temperature on enzyme action

• Increasing temperature increases enzyme action, as molecules have a higher kinetic energy and there are more successful collisions between enzyme and substrates.

• Above a certain temperature, the shape of the active site is altered and the enzyme becomes denatured, so it can no longer catalyse the reaction.

Effect of pH on enzyme function

The optimum pH for most enzymes is 7 (apart from proteases in the stomach).

• If the pH is too extreme, the shape of the active site may be altered and the enzyme may no longer work.

Production sites of carbohydrases, proteases and lipases

Carbohydrases - Salivary gland, stomach and small intestine.

Proteases - Stomach, pancreas and small intestine.

Lipases - Pancreas and small intestine.

Role of carbohydrases in the digestive system

Carbohydrases break down carbohydrates into glucose.

Amylase breaks down starch into glucose.

Proteases

Proteases break down proteins into amino acids.

Lipases

Lipases break down lipids into fatty acids and glycerol.

Where is bile made and stored?

Bile is made by the liver and stored in the gallbladder.

Role of bile in the digestive system

Bile is an alkaline substance which neutralises the hydrochloric acid secreted by the stomach. Bile emulsifies lipids (fat)

Food test for sugars and positive test colours

Food tester: Benedicts (blue)

Positive for sugar:

• Small amount: Blue → Green

• Bigger amount: Blue → Yellow

• Large amount: Blue → Brick-red

Food test for proteins and positive test colour

Food tester: Biuret (blue)

Positive for protein:

• Blue → Purple/Lilac

Food test or lipids (fats) and positive test colour

Food tester: Ethanol (clear)

Positive test for lipids:

• Clear → Cloudy emulsion

Heart

An organ that pumps blood around the body.

Purpose of the circulatory system

Carries oxygen and other useful substances to bodily tissues, and removes waste substances.

Double circulatory system

One pathway carries blood from the heart to the lungs - where the gaseous exchange of oxygen and carbon dioxide takes place. One pathway carries blood from the heart to the tissues.

Importance of the double circulatory system

It makes the circulatory system more efficient - E.g. oxygenated blood can be pumped around the body at a higher pressure by the left ventricle.

Chambers of the heart

4 - right atrium, right ventricle, left atrium, left ventricle.

Heart circulation steps

1. Vena cava brings deoxygenated blood from the body to the heart.

2. Passes from heart to the lungs in the pulmonary artery.

3. In the lungs, blood collects oxygen.

4. Oxygenated blood passed from the lungs to the heart in the pulmonary vein.

5. This blood is pumped from the heart to the body in the aorta.

6. Oxygen is transported around the body and cycle repeats.

Pumping of blood in heart steps

1. Blood enters left atrium and right atrium.

2. Atria contract and blood is forced into the ventricles.

3. Ventricles contract and force blood out of the heart.

   Valves prevent back flow of blood when ventricles contract.

   Left ventricle has a thicker muscular wall as it must pump blood around body at higher pressure.

Specific role of the left ventricle?

Pump blood at a higher pressure around the whole body.

What is the function of the aorta?

Carries oxygenated blood from the heart to the body.

What does the pulmonary vein do?

Carries oxygenated blood from the lungs to the heart.

What is the role of the vena cava?

Carries deoxygenated blood from the body to the heart.

What does the pulmonary artery carry?

Carries deoxygenated blood from the heart to the lungs.

Purpose of valves in the heart

Prevent the backflow of blood.

Purpose of coronary arteries

Coronary arteries supply the heart muscle with oxygenated blood.

Control of heart rate

Controlled by a group of cells in the right atrium which act as a pacemaker by releasing waves of electrical activity which causes the heart muscle to contract.

How is irregular heart rhythms treated?

Using an artificial pacemaker, which sends out electrical signals to correct the heart's rhythm.

Types of blood vessels

Arteries, Veins, Capillaries.

Arteries function and adaptation

Function: carry blood away from the heart.

- Thick muscle layer: adds strength to withstand high pressure.

- Thick elastic layer: allows arteries to stretch and recoil to withstand high pressure.

Veins function and adaptation

Function: carry blood towards the heart.

- Wide lumen: enables low pressure.

- Valves: prevent backflow of blood.

Capillaries function and adaptation

Function: enable transfer of substances between the blood and tissues.

- Walls are one cell thick: short diffusion path.

- Permeable walls: substances can diffuse across.

- Narrow lumen: blood moves slowly, more time for diffusion.

Rate of blood flow calculation

Volume of blood / number of minutes.

Gas exchange system components

Trachea, Bronchi, Bronchioles, Alveoli

Lung ventilation process

1. Air passes into lungs through the trachea

2. Trachea splits into two smaller tubes, bronchi, passing to each lung

3. Bronchi subdivide into many smaller tubes, bronchioles

4. Bronchioles end in alveoli

5. Gases diffuse in a out of bloodstream at the alveoli

Gas exchange at the alveoli

Oxygen diffuses from the alveoli into the capillary bloodstream down its concentration gradient. Carbon dioxide diffuses from the capillary into the alveoli down its concentration gradient.

Alveoli adaptation for gas exchange

- Larger surface area

- Rich blood supply: maintains concentration gradient.

- Thin walls: short diffusion pathway.

Substances transported by plasma

Red blood cells, White blood cells, Platelets, Carbon dioxide, Urea, Products of digestion.

Definition of plasma

A yellow liquid within blood that transports substances around the body.

Purpose of red blood cells

Transport of oxygen around the body.

Red blood cells adaptation

- Biconcave shape: increased surface area to volume ratio.

- No nucleus: more room haemoglobin and therefore oxygen.

- Contain haemoglobin: binds to oxygen.

Purpose of white blood cells

They form part of the immune system, which protects the body from invading pathogens.

Nucleus

Contains DNA which codes for proteins.

Platelets

Small cell fragments which aid the clotting of blood at the site of a wound.

Blood clotting

The process where platelets aid in the conversion of fibrinogen to fibrin, trapping red blood cells to form a clot.

Coronary heart disease

Occurs when the coronary arteries that supply the heart muscle become blocked with a buildup of fatty material.

Stent

A tube that is inserted into a blocked artery to keep it open.

Advantages of stents

• quick recovery time

• lower the risk of a heart attack.

Disadvantages of stents

• Risk of infection

• risk of blood clots at the site of stent.

Statins

Drugs which reduce the level of (bad) cholesterol in the blood.

Advantages of statins

• Reduce risk of strokes, coronary heart disease and heart attacks

• increase level of (good) cholesterol.

Disadvantages of statins

Have to be taken continuously, may have side effects, effect may not be immediate.

Heart bypass surgery

A surgery where blocked coronary arteries are replaced with sections of veins taken from other parts of the body.

Leaky heart valves

Cause blood to flow in the wrong direction, making the heart less efficient.

Mechanical valves

Valves made of metal used to replace leaky valves.

Biological valves

Valves taken from animals (pigs, sometimes humans) used to replace leaky valves.

Advantages of mechanical valves

Last for a very long time.

Disadvantages of mechanical valves

Need to take medication to prevent blood clotting around valve.

Advantages of biological valves

Work very well - no medication required.

Disadvantages of biological valves

Only lasts 12-15 years.

Artificial heart

Intended to support a patient's heart while they wait for a suitable donor heart.

Advantages of artificial hearts

• Less likely to be rejected by immune system

• allows damaged heart to rest to help recovery.

Disadvantages of artificial hearts

• Risk of infection due to surgery

• risk of blood clots

• have to take blood-thinning drugs.

Health

The state of physical and mental wellbeing.

Alcohol effect on liver and brain function

• increases risk of liver cirrhosis and liver cancer

• affects the brain, leading to addiction and memory loss.

Smoking effect on lung disease and cancer

• Tar in tobacco can damage the alveoli of the lungs.

• Tar also damages the cells which line the lungs, leading to lung cancer.

• Cigarette smoke contains chemicals like carcinogens which trigger cancer.

Smoking and alcohol effect on unborn babies

Smoking when pregnant increases risk of miscarriage and premature birth. Also can lead to low body-mass in babies.

Alcohol may cause babies to be born with fetal alcohol syndrome, leading to learning difficulties and other mental / physical problems.

Cancer

Cancer is the development of a tumour as a result of uncontrolled cell division.

factors leading to cancer

Genetics.

Smoking.

Obesity.

Viral infections.