Tissues and Organs

Group of cells

Tissues Organs Systems Organism

Tissues

• Cells differentiate (change their shape and

structure to perform a specific job or function)

• A group of specialised cells that perform one or

more particular function is called a tissue e.g.

– Phloem tissue in plants transports food

– Muscle tissue is made up of similar cells that can

contract and relax

• A tissue can also consist of a mixture of

specialised cells e.g. blood tissue

• Study of tissues is called histology

Organs

• Many tissues grouped together to make a

structure with a special function e.g.

– Leaf: epidermal, palisade, mesophyll, xylem and

phloem tissue

– Stomach: muscle, connective, epithelial, nerve and

blood tissue

Systems

• A group of organs whose functions are closely

related e.g.

– A plant shoot: leaves, stems and buds

– Nervous system: brain, spinal cord and nerves

• A plant or animal that is made up of cells,

tissues, organs and systems that work together

e.g. plant or human

Organisms

Animal Tissues

Animal cells with the same

structure and function are

organized into tissues and

consist of four main types

1. Epithelia

2. Connective

3. Muscle

4. Nerve

Epithelial tissues• Similar to epidermis in plants

• Covers the body on the outside and lines the internal cavities, passages and tubes in the body

• Usually separated from the underlying tissue by a thin sheet of connective tissue called the basement membrane

• Epithelial cells are packed tightly together and contain few intercellular air spaces

• Is also called epithelium. The epithelial tissue that lines internal body surfaces is called endothelium

• All epithelial tissues consist of a single layer of cells found on a basement membrane.

• Main Function: Protect the underlying tissues from injury,

friction, harmful substances, loss of water and invasion

of micro-organisms

• Other functions:

▪ Secretes chemical substances e.g. epithelial tissue in

glands

▪ Absorbs nutrients e.g. in the small intestine

▪ Removes dust and foreign particles from the air

passages

▪ Excretes waste products e.g. sweat from skin

4 Types of Epithelial: 1. Squamous epithelium: thin, tightly packed, irregular

cells. Lining the mouth, oesophagus, alveoli and

blood vessels. Protects the underlying tissues and is

permeable to certain substances e.g. gas in the

alveoli. (Fig 4.22 pg 103)

2. Columnar epithelium: elongated cells that contain an

oval shape nucleus near the bottom of the cell. Lines

the intestine and gall bladder. In the villi (small

intestine) goblet cells that secrete mucus occur

between the columnar cells. Columnar epithelium

supports other cells e.g. absorption of food, water,

vitamins, minerals and salts (Fig 4.24 pg 103)

3. Ciliated epithelium: consists of columnar epithelial cells

that have cilla on the exposed surface of the cells. Lines

the trachea, nasal cavities, bronchi and contains goblet

cells. Cilia trap dust and other particles in the air passages

and the mucous secreted by the goblet cells protects the

alveoli. (Fig 4.25 pg 104)

4. Cuboidal Epithelium: Square shaped. Each cell has a

spherical nucleus in the center of the cell. Lines many of

the glands of the body. Have a secretory function e.g.

secrete sweat or oil. (Fig 4.26 pg 104)

Connective tissue• Main function is to support and join other tissues

• Consist of a small number of living cells embedded in a

large amount of non-living ground substance (matrix).

• Matrix can be liquid (blood), jelly-like (areolar) or solid

(bone)

• Types include adipose (fat) tissue, areolar tissue,

ligaments, tendons, cartilage, bone and blood.

• Blood is the only form of connective tissue in liquid form

• Matrix (plural:

matrices) is the

material (or tissue) in

animal or plant cells,

in which more

specialised structures

are embedded.

3 Types of Connective Tissue…

Areolar Tissues

• Padding tissue / connective tissue proper

• Most common tissue in the body

• Forms a continuous layer under the skin

• Fills up spaces between organs and muscles

(packing tissue)

• The jelly-like matrix contains fibres and cells

– Fibres are yellow elastic and white non-elastic fibres

– Cells are fibroblasts, macrophages, mast and fat cells

Areolar Tissues

• Tendons are a

connective tissue with

lots of white non-

elastic fibres.

Tendons connect

muscle to bone and

must be inelastic to

transmit the muscle

movement to the

bone.

• Ligaments are a

connective tissue with

lots of yellow elastic

fibres. Ligaments

connect bone to bone

so must be elastic to

allow joint to move.

Cartilage and Bone

• Make up the endoskeleton of animals

• Living tissue consisting of cells (chondrocytes in

cartilage and osteocytes in bone). Cells secrete

the intercellular matrix

• Bone is hard and rigid

• Cartilage is tough and flexible.

Cartilage

• 3 types: hyaline, white fibrous and yellow elastic

• Each cartilage has a slightly different structure

and function

• Chondrocytes found in fluid-filled spaces called

lacunae

• 1, 2 or 4 chondrocytes per lacunae

• Chondrocytes secrete the rubbery matrix which

is mainly a protein called chondrin

Bone Tissue

• The outer membrane of bone is called the periosteum

• Osteocytes found in lacunae

• Lacunae are concentric circles around a central canal called the Haversian canal.

• Blood vessels and nerves are found within this canal

• Osteocytes secrete the matrix which contain collagen fibres hardened by calcium

• The matrix is called lamellae

• Tiny canals linking lacunae are called canaliculi

• Haversian canal + lacunae = Haversian system

• Nutrients, oxygen and waste are transported

through the canal and canaliculi because the matrix

is impermeable

• Bones protect the internal organs, gives shape to

the body and serves as attachment points for

muscles

• Muscles and bone work together = Movement

Blood consists of

• Red blood cells (erythrocytes) – they do not have a nucleus (not

real cells) and are round biconcave discs. They contain the

pigment haemoglobin in cytoplasm (red). Combines with oxygen to

become oxyhaemoglobin. Transfers oxygen from the lungs to the

body. RBC are flexible and have a very large surface area

• White blood cells (leucocytes) – they have one or more nuclei

present and they produce antibodies that fight infection by

destroying pathogens. They can move into tissues (amoeboid) and

engulf bacteria and foreign particles

• Platelets are fragments of red blood cells – they help form blood

clots to minimise blood loss

• Plasma is the fluid component of blood - consists mainly of water

and dissolved substances (salts, hormones, vitamins, nutrients and

plasma proteins) – plasma transports these substances around the

body

Muscle Tissue

• A special type of tissue that can contract or relax

• The elastic nature enables animals to move

• Muscle cells are called fibres and are bound

together into sheets or bundles

• There are three types of muscle tissue

3 Types of muscle tissue

1. Striated/ Striped/ Voluntary/ Skeletal muscles:

• Muscles attached to some part of skeleton by tendons.

• Contraction of these muscles bring about voluntary

movement of the body e.g. walking, running.

• Contains long muscle fibres that are made up of smaller

units called myofibrils

• Each muscle fibre contains more than one nucleus

2. Unstriated/ involuntary/ smooth muscles

• Found on the walls of blood vessels, intestine, uterus, bladder.

• They control involuntary movements e.g. in the intestine they bring about peristalsis

• Contain thin spindle shaped muscle fibres

• Each muscle fibre contain a single nucleus

• Contracts slower than skeletal, but is able to maintain contractions longer

3. Cardiac Muscles:

• Found only in the walls of the heart and control involuntary movement of your heart beating

• They contract and relax continuously (maintaining rhythm of your heart)

• Responsible for the pumping action of the heart

• Each muscle fibre contains a single nucleus. Fibres are branched.

• Also striped but not as clear as in voluntary muscles

• Nerve cells are known as

neurons and are the basic

unit of nerve tissue.

• Neurons made up of 2 types

of nerve fibres: Axons and

Dendrons and a cell body.

• Cell body contains

organelles, cytoplasm and

nucleus.

• Cell body contains Nissl

bodies (transmits impulses)

• The nerve fibres conduct and

transmit nerve impulses

throughout the body

Nervous tissue

Nervous tissue

• Nervous tissue makes up the brain and spinal cord

• 3 types:– Sensory neurons

– Motor neurons

– Interneurons

• Dendrite: impulses toward the cell body

• Axon: impulses away from the cell body

• Axon can be over 1 m long

• Axon covered by myelin sheath (fatty sheath) –insulator and speeds up transmission of impulses

• Neurilemma covers myelin sheath and is interrupted by nodes of Ranvier

3 types of neurons

• Sensory neurons:

transmit information

from receptors e.g.

skin, eyes, nose to

the central nervous

system (brain and

spinal cord)

Motor Neurons

• Transmit information

from the Central

Nervous System to

the effectors e.g.

Muscles or glands

Interneurons

• Connect sensory and

motor neurons

• Found within the brain

or spinal cord

Biotechnology and indigenous

knowledge systems

• Indigenous knowledge

• Immunity

• Vaccines

• Blood types

• Blood transfusions

• Cloning