1. Topic 6: Human health and physiology 1
6.1- Digestion:
Ingestion- you eat the food
Digestion- a series of chemical reactions, whereby you convert the ingested food to smaller and
smaller molecular forms
Absorption- small molecular forms are absorbed through cells of your digestive system and pass
into nearby blood or lymphatic vessels
Transport- your circulatory system delivers the small molecular nutrients to your body cells
Many of the foods we ingest have very large molecules, too large to pass across the cell
membrane. But in order for the food to get into your bloodstream, molecules must pass through
the cell membrane of your intestines and then through the cell membrane of a capillary.
Therefore any food we intake must be chemically digested into a suitable size. Plant cells
characteristically store excess carbohydrates in the form of starch, whereas animals store excess
carbohydrates as glycogen. Each type of living organism has its own unique set of proteins.
The role of enzymes during digestion:
Enzymes are biological catalysts- globular proteins that increase the rate of a reaction by
lowering activation energy. Digestive enzymes are released into the gut from glands and are
used in catabolic reactions- they break down larger molecules. By lowering the activation energy
of the reaction, the reaction does not require high temperature. By using an enzyme, reaction
can occur more quickly at body temperature. Some examples of digestive enzymes are Salivary
amylase, Pepsin (a protease), and Pancreatic lipase.
Stomach:
Food is brought to your stomach by a molecular tube called the oesophagus. Gastric juice is a
mixture of three secretions from the cells of the stomach inner lining.
Pepsin- a protease enzyme most active in acidic pH
Hydrochloric acid- helps degrade and break down foods and create the acidic pH
necessary for pepsin to be active
Mucus- lines the inside of the stomach wall to prevent stomach damage from the
hydrochloric acid
Small intestine:
The first portion of the small intestine is called the duodenum.

2. These secretions include:
Bile from the liver and gall bladders
trypsin ( a protease) lipase, amylase, and bicarbonate from the pancreas
The digestive process continues in the small intestines, molecules are produced that are
small enough to be absorbed.
Inner wall of the small intestine is made up of thousands of finger like extensions called villi.
Most of the molecules absorbed are taken into the capillary bed within each villus.
Large intestines:
The vast majority of useful nutrients are absorbed while food is still inside the small intestines.
What remains of the original food at the end of the small intestines is undigested. Much of the
water that we drink or that is naturally contained in many foods is still present. The primary
function of the large intestine is water absorption. The large intestine is also home to a very
large member of large intestines of naturally occurring bacteria, including Escherichia coli.
These bacteria are examples of mutualistic organisms within us. We provide nutrients, water,
and a warm environment while synthesize vitamin K and maintain a healthy overall
environment for us in our large intestine.

3. 6.2: The transport system
The human heart is designed as a pair of side by side pumps. Each side of the heart has a
collection chamber for blood that is moving slowly and from the veins. Theses thin walls, must
cular chambers are called atria each side also has a thick wall, muscular pump(called a ventricle),
this builds up enough pressure to send the blood out from the heart with a force called blood
pressure. The double sided pump work every minute of every day of your life. Blood pump out
from the heart usually makes a circuit through following range of blood vessels.
A large artery
Smaller artery branches
An arteriole (smallest type of arteria)
A capillary bed
A venule( cmallest type of vein)
A large vein
Larger veins
The two sides of the heart allow for there being two routes for blood to flow along . The right
side of your heart allows for blood to be routed called you pulmonary circulations.
The capillary bed is in one lung, and blood picks up oxygen and releases carbon dioxide. He left
side of the heart sends blood along a route that is called you systemic circulation. On this route
the capillary bed is in one organ or tissue and picks up co2 releasing oxygen
Pulminary Circulation This contraction initiates several events:
Closure of the atrioventricular valve to prevent back flow to the right atrium ( closing of
valve produces ‘lud dub’
Increase in blood pressure opens right semi lunar valve
Due to the increase in pressure blood leaves the heart through the pulmonary artery
Systemic circulation
Closure of the atrioventricular valve to prevent back flow into the left atrium
Dramatic increase in blood pressure inside the left ventricle which opens the left semilunar
valve and allows blood to enter aorta
Due to increase in pressure, blood leaves the heart through aorta
Control of Heart Rate
The majority of the tissue making up the heart is muscle. The right atrium of tissues within its walls
known as the sinoatrial node. This mass of tissue acts as peace maker for the heart. It sends out an
electrical signal to initiate the contraction of both atria.
Arteries capillaries and veins-
Arteries are blood vessels taking blood away from the heart that has not yet reached a capillaries

4. Veins are blood vessels that collect blood from capillaries and return it to the heart.
Arteries have a relatively thick smooth muscle layer that is used autonomic nervous system to
change the inside diameter of the blood vessels. This helps to regulate blood pressure.
Blood in arteries were at high pressure as arteries directly ventricles of the heart.
Much of the pressure is lost. Blood cells make their way though capillaries one cell at a time. Veins
receive blood at low pressure from capillary beds. Because this blood has lost a great deal of blood
pressure, the blood flow through veins is slower through arteries
6.3 Defence Against infectious disease
Pathogens cause disease
Any living organism or virus that is capable of causing a disease is called a pathogen. Pathogens
include viruses, bacteria, protozoa fungi and warts of various types.
How antibiotics work against bacteria
Bacteria are prokaryotic cells and our bodies are eukaryotic cells. The difference between the two
types of cells are biochemical reactions and pathways. One type of antibiotic may selectively block
protein synthesis from bacteria, but has no effect on our body cells