tissues and organs - wordpress.com...2018/08/06 · systems • a group of organs whose functions...
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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