Nat5 Biology - Key Area 2.6 + 2.7

What is blood composed of?

Blood is composed mostly of a watery, yellow substance called plasma.

What does plasma carry?

Plasma carries white and red blood cells.

What is the main role of blood?

The main role of blood is to transport nutrients, oxygen and carbon dioxide around the organism.

What is the role of red blood cells?

The role of red blood cells is to carry oxygen to aerobically respiring cells within the body. They are specialised to do this.

How are red blood cells specialised for their role?

They have a biconcave shape (large surface area), they contain Haemoglobin (a red protein that combines with oxygen - more haemoglobin = larger quantities of oxygen), they have no nucleus.

oxygen + haemoglobin

Oxyhaemoglobin (reversible)

What does haemoglobin rapidly combine with to form oxyhaemoglobin?

Haemoglobin rapidly combines with oxygen to form oxyhaemoglobin.

When oxygen is needed, what happens?

When oxygen is needed, it is released to respiring cells and turns back into Haemoglobin.

They have a biconcave shape

Increases the surface area for the absorption of oxygen

They have no nucleus

Increases the cells ability to carry more oxygen

Haemoglobin in the cytoplasm of the red blood cell

Rapidly combines with oxygen to form Oxyhaemoglobin

TIP

Don't refer to red blood cells as RBC

How many chambers does the heart have?

The heart has 4 chambers: 2 atria and 2 ventricles.

How many valves does the heart have?

The heart has 4 valves.

What is the purpose of valves?

Valves help to prevent the backflow of blood and make sure that the blood flows in one direction.

Veins

Veins carry deoxygenated blood at low pressure into the heart.

Arteries

Arteries carry oxygenated blood at a high pressure away from the heart.

right side of the heart

deoxygenated blood (low oxygen, high carbon dioxide)

left side of the heart

oxygenated blood (high oxygen, low carbon dioxide)

Coronary Arteries

The coronary arteries supply the heart muscle with oxygen rich blood and nutrients. This allows the muscle cells of the heart to respire and produce energy for contraction and relaxation (beating).

Structure of Arteries

(thick, muscular walls) and (narrow central channel)

Structure of Veins

(thin walls), (wide channel), (valves)

Capillary function

Capillaries form networks at tissues and organs to allow efficient exchange of materials.

Structure of Capillaries

(thin walled), (large surface area)

How thick are capillary walls?

Capillary walls are only one cell thick allowing rapid diffusion.

Pro tip about Capillaries

It is a capillary wall NOT a cell wall.

What are pathogens?

Pathogens are disease-causing viruses, bacteria and fungi which can infect animals and plants.

How does our body recognise pathogens?

All cells have antigens on their surface. The antigens on the pathogens surface are recognised as 'foreign' by the human immune system and an immune response begins.

Immune system

The immune system consists of a vast number of cells, organs, proteins and tissues throughout the body.

Where are white blood cells produced from?

The immune system

How do white blood cells fight infections?

White blood cells fight infection by producing two different types of cells: phagocytes and lymphocytes.

Phagocytes

If a pathogen is identified, the phagocyte will engulf and destroy it. This process is called phagocytosis. Phagocytosis translates to 'cell eating'.

Lymphocytes

Lymphocytes produce antibodies to destroy pathogens. Each antibody is specific to a particular pathogen and attaches to the receptor on its surface.

Special thing about antibodies

Each antibody is specific to a particular pathogen due to the shape of the receptor at the end of the antibody. This makes sure that the immune system is specific to the foreign pathogen.

Why do we need absorption?

Oxygen and nutrients from food must be absorbed into the bloodstream to be delivered to cells rapidly. Waste materials, including carbon dioxide, must be removed from cells into the bloodstream and exhaled through the lungs.

Capillary networks

Tissues contain capillary networks to allow the exchange of materials at cellular level.

Materials absorbed in animal cell

oxygen and glucose

Materials excreted in animal cell

carbon dioxide

Materials absorbed in plant cell

carbon dioxide + water

Materials excreted in plant cell

oxygen and glucose

Materials absorbed in yeast cell

glucose

Materials excreted in yeast cell

ethanol/alcohol and carbon dioxide

How do we breathe?

As you breathe in, air moves down the Trachea to the Bronchus, which is split into 2 Bronchi. Air moves from the Bronchi to the Bronchioles down into the Alveoli.

Where does gas exchange occur?

Alveoli

Alveoli

Each alveoli is surrounded by a network of blood capillaries.

How does gas exchange occur?

Gas exchange takes place between the air inside the alveoli and the blood carried by the surrounding capillaries. Blood arriving at the alveoli from the heart contains a lower concentration of oxygen than the air delivered to the alveoli. This creates a concentration gradient. Oxygen will move from the alveoli into the blood by diffusion and travel to the heart.

What features do alveoli have which make them specially adapted to increase the rate of gas exchange?

Alveoli are moist (to allow oxygen to dissolve), have thin alveolar walls (rapid diffusion), large surface area (larger area for gas exchange), surrounding capillaries are also only one cell thick (rapid diffusion).

What does the small intestine contain?

The small intestine contains millions of finger-like projections called villi (villus).

What is the purpose of villi?

The large number of thin walled villi provides a large surface area for rapid absorption.

What does each villi contain?

Each villus contains a network of Blood Capillaries to absorb glucose and amino acids and a lacteal to absorb fatty acids and glycerol.

Comparing absorption in the villi and alveoli

These are: large surface area, thin wall and an extensive blood supply.