chapter 1 -2013 animal tissues

7/27/2019 Chapter 1 -2013 Animal Tissues

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CHAPTER 1 - CELL AS UNIT OF LIFE

1.4.2 Animal cell

multicellular animals are made up of a number of different types of cells

it made the organism more effective in carrying out different activities as different cells are

specialized to carry out different functions

CELL TISSUES ORGANS SYSTEMS

ANIMAL TISSUES I. Epithelium a) Simple

b) Stratified

c) Pseudostratified

II. Connective a) Cartilage

b) Bone

c) Blood

III. Muscle a) Striated (voluntary/skeletal)

b) Smooth (Involuntary/unstriated)c) Cardiac(heart)

IV. Nerve

l) Epithelium

covers the outer layer of the skin and all surfaces inside the body

general characteristics;i) cells are arranged close to each other forming a continuous layer

ii) there are two surfaces, one exposed and the other are attached to the basementmembrane

Its importance:i) for protection, secretion and as sense organsii) controls the exchange of materials between different part of the organisms and the environment

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a) SimpleEpithelium

i) Simple squamous epithelium

- flat cell, disc shaped nucleus, little cytoplasm- in alveolus and capillary blood vessel

- function in providing a thin layer across which diffusion can occur

ii) Simple cuboidal epithelium

- cell is cube-shaped, central spherical nucleus- lines the kidney tubule and many exocrine glands/ ducts- function in secretion and absorption as cells are rich in specific transport

channels

iii)Simple columnar epithelium

- cells tall and narrow with nucleus at the basal end.- Possess a lot of Golgi apparatus and might have cilia, microvillus or form gobletcells which produce mucus.

- Lines the digestive and respiratory system- Function in secretion, absorption, protection and production of mucus

b) StratifiedEpithelium

i)Stratified squamous epithelium

- a few layers of cell whereby the lower layer will replace the old and worn outcells of the upper layer

- found in the skin, mouth cavity and vagina function in protection and incellreplacement

ii)Stratified cuboidal epithelium

- 2-3 layers of cuboid-shaped cells- found on the surface of the exocrine glands/ ducts.

iii)Stratified columnar epithelium

- 2-3 layers of cells, with cells at the topmost layer shaped like a column

found in the pharynx, larynx, mammary glands and salivary glands

c) PseudostratifiedEpithelium

columnar shaped cells of varying heights, all cells are attached to the

basement membrane but not all are exposed to the surface may be ciliated, have microvillus or glands.

found in certain parts of the respiratory tract and secretory duct

functions in secretion, protection and transport of mucus


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II) Connective Tissue

made up of three components;

No. Component Characteristics

i) Cells - Usually there are a numberofcells in one type of connective tissues

ii) Matrix - Secretedby the connective cells. Can exists in the form of liquid,

semi-

liquid orsolid

iii) Fibers - Found in the matrix and produced by the connective cells

- Usually there are 3 types of fibers

collagen- strong and not easilybent

elastic- easily stretched

reticulate- fine and branching, therefore acts as a supporting net.

a) Bone Tissue

Consists of a hard and rigidmatrixmade up of calcium phosphate (in the form ofhydroxyapatite crystals) and collagen fibers (strong yet flexible).

Matrix consists of numerous cylinders called the Haversian system. Each cylinder is made up ofconcentric layers called the lamella. Between the lamella are munerous lacunae (a space filledwith tissue fluid) containing osteocytes (bone cells) which secrete the matrix.

There is a harvesian canal in the middle of the haversian system and it contain

nerve and blood capillaries to supply the osteocytes with nutrients etc.

Osteocytes are connected to each other through cytoplasmic strands in canaliculi.

Volkmann's canal connects the harvesian systems.

Function in support and protection, source of Ca + and place for muscle attachment

b) Cartilage Tissue

Possess a light bluish matrix called chondrin (made ofprotein-polysaccharides).Chondrin are strong and elastic.

Chondrocytes (cartilage cells) located in the matrix lacunae, secrete the chondrin.

Chondrin does not have blood vessels, nerves or lymphatic vessels. Nutrient supply comes fromthe perichondrion outside the cartilage and it diffuses through the chondrin into the

chondrocytes. chondrin have collagen fibers to add strength of the cartilage

Eg. Hyaline cartilage

found in the C-shaped rings of the trachea, ear, nose and at the end of longbones

function in support, shockabsorption and to reduce friction between bones.

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III) Muscle Tissue

there are 3 types of muscles

a) Striated muscles (voluntary/ skeletal)

made up of hundred of cells ormuscle fibers shaped like a cylinder, arranged parallel to eachother and has a diameter of 50m. Each muscle fiber has many nucleuses at its sides. It issurrounded by cytoplasm called sarcoplasma and enveloped by a membrane calledsarcolemma. There is also a system of membrane called the sarcoplasmic reticulum.

Muscle fibers have a lot ofmyofibrils with a series of light and dark bands.

Myofibrils are made up of 2 types of proteins, actin (thin filaments) and myosin

(thick filaments).

Striated=muscles are found in the diaphragm, abdominal wall and muscles used

for movements

b) Smooth (involuntary/ unstriated)

No light and dark striation

Spindle-shaped cells with one nucleus at the center

Involuntary and rhythmic movement

Found in digestive tracts, blood vessels and urinogenital system

c) Cardiac (heart)

Made up of short cells or fibers, cylindrical-shaped, and joined end-to-end through intercalated

discs

The fibers are branched, nucleus in the middle and presence ofsarcolemma and sarcoplasma

Myofibrils can be seen to have light and dark bands

Only found in the heart and it is myogenic in nature

IV) Nerve Tissue

Made up of neurons and neuroglial cells

i) Neuron

- contain cytoplasm, nucleus, Nissl granules (for protein synthesis) etc.- possess dendrites that function in sending impulses to the cell body- there is a long axon which function to send impulse out of the cell body.Axon terminals end with structures called synapse.

- There is myelin sheath formed by the Schwann cell enclosing the axon except at the

Ranviernodes. Neurilemma forms the outer layer of the myelin sheath

ii) Neuroglial cells

- supporting cells surrounding the neurons- non-excitable and_do not conduct impulse

- play a supportive and protective role to the neurons- eg. Schwann cells which wrap themselves around neurons forming concentric

layers called the myelin sheath.

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chapter 1 -2013 animal tissues

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