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Tissues
• In most multi-cellular organisms, groups
of cells of the same type associate
together to form tissues.
• The cells in a tissue act together to
perform a common function.
• Working as a group of cells is more
efficient than working individually.
Types of tissues
• In the human body there are 4 main types of
tissue contributing to homeostasis.
• They provide protection, support,
communication between cells and resistance
to disease.
• The 4 main types are:1. Epithelial
2. Connective
3. Muscle
4. Nervous
Structure of Epithelial tissues
• Epithelial tissue covers the whole surface of the
body.
• It is made up of cells closely packed and ranged
in one or more layers.
• Epithelial cells are packed tightly together, with
almost no intercellular spaces and only a small
amount of intercellular substance.
• Epithelial tissue, regardless of the type, is usually
separated from the underlying tissue by a thin
sheet of connective tissue; basement membrane.
• The basement membrane provides structural
support for the epithelium and also binds it to
neighbouring structures.
Types of epithelial tissues
• Epithelial tissue can be divided into two
groups depending on the number of
layers of which it consists.
• Epithelial tissue which is only one cell
thick is known as simple epithelium.
• If it is two or more cells thick such as
the skin, it is known as stratified
epithelium.
Simple epithelium
• Squamous epithelium
• Flat, thin plates to allow rapid movement of
substances through them.
• found in the mouth, blood vessels, heart and
lungs.
Simple Cuboidal
• Cuboidal in shape. Each cell has a spherical
nucleus in the centre.
• May have microvilli on the surface to aid
secretion and absorption.
Simple columnar
• Cells are elongated.
• Nuclei are also elongated and are usually
located near the base of the cells
Ciliated Columnar
• Cuboidal cells with cilia
or hairs which assists
the movement of
substances and
secretions along the
tissue.
• Found in the respiratory
tract and in the
Fallopian tubes.
Compound epithelium
• Where body linings have to withstand
wear and tear, the epithelia are
composed of several layers of cells.
• The cells may be simple as described or
keratinised.
• Keratin is a tough fibrous protein that
helps protect the skin and underlying
tissues from heat, microbes that may
cause infections and disease and
chemicals.
Connective tissue
• Widely distributed in the body.
• Made up of cells and matrix.
• Matrix fills the spaces between cells
and consists of protein based fibres
secreted by the connective tissue cells.
• Connective tissue binds together,
supports and strengthens other body
tissues.
• Provides protection and insulation to
internal organs.
Blood
• Fluid connective tissue.
• Function = major transport system within the
body.
• Made up of a number of different blood cells:1. Red blood cells (erythrocytes)
2. White blood cells (leukocytes)
3. Platelets (thrombocytes)
4. Plasma (the matrix)
Cartilage
• Differs from other types of connective tissue
as it has no blood or nerve supply.
• Closely packed network of collagen and elastic
fibres.
• Found where bones meet e.g. at joints.
• Acts as a shock absorber.
Bone
• Much harder than cartilage, but can be worn away
by friction.
• Bone is made up of calcium salts and collagen fibres.
• Hardness of bones is due to the density of calcium
within the bone matrix.
• Bone strength derives from the collagen fibres.
Areolar Tissue
• Most common type of tissue in the body.
• Binds muscle groups, blood vessels and nerves
together.
• Contains collagen, elastic and reticular fibres.
• Elastic fibres provide flexibility.
Adipose tissue
• Loose connective tissue with specialised fat storage
cells.
• Commonly found under the skin and around vital
organs such as the heart, kidneys and parts of the
digestive tract.
• It insulates against external temperature changes
and acts as a hydraulic shock absorber to protect
against injury.
Muscle tissue
• Main function of muscle tissue is to
change chemical energy into mechanical
energy in order to produce force,
perform work and produce movement.
Smooth muscle (Non-striated)
• This is called involuntary muscle.
• It is called smooth muscle because you cannot
see any stripes when you look at it through
the microscope, and it’s called involuntary
muscle because you cannot make it contract
and relax through conscious control. Smooth
muscle contracts and relaxes automatically.
• This muscle is found in the gut and in the iris
of the eye.
Skeletal muscle (Straiated)
• This is called voluntary muscle or striped muscle. It is called
striped muscle because it has a striped appearance when
viewed through a microscope. It is called voluntary muscle
because you have direct control over this type of muscle
when you want to make a movement.
• Skeletal muscle is the muscle attached to your bones. You
have direct control over these muscles and can make a large
range of movements. Skeletal muscle is also found in your
face and jaws, so it is used when you smile or frown and when
you talk, eat or drink.
Cardiac muscle
• Cardiac muscle- This is also involuntary, but
looks different under the microscope as it has
a striped appearance and many
interconnecting bridges. Cardiac muscle
contracts and relaxes automatically without
you having to think about it. Cardiac muscle is
myogenic.
Nervous tissue
• Found in the central nervous system (CNS) or
in the peripheral nervous system (PNS).
• Nervous tissues are composed of 2 parts,
mainly neurones and neurogia.
Neurones
• Sensitive to stimuli.
• They convert stimuli into nerve impulses and
relay them to muscle tissue or glands, in order
for the body to respond.
Neurolgia
• Do not generate or conduct nerve impulses.
• They act as glue to hold the nervous system
together.