Animal tissue

Animal body is made up of four main types of tissues;

• epithelial tissue
• connective tissue
• nerve tissue
• muscular tissue

 

 

• Covers the internal or external surface of the organism
• Arranged in single or many layers

 

Features found in the epithelial tissues;

• Covers the free surface of the body
• supported by basement membrane
• not supplied with blood vessels
• free now endings are found
• lacks intercellular spaces or absent
• ectodermal and endodermal origin
• intercellular matrix is made up of hyaluronic acid
• free service of the epithelial tissues may contain cilia and flagella

 

Major functions of epithelial tissues

• protection from mechanical injuries, infection, desiccation and friction
• secretion
• absorption
• filtration

 

Simple squamous epithelium

• flattened cell
• thin flattened Central nucleus
• Location;
  • blood capillaries alveoli and lymph capillaries are made up of simple squamous epithelium only
  • endothelium of blood vessels heart and lymph vessel
• function;
  • diffusion
  • lubrication

 

Simple cuboidal epithelium

• cuboidal shaped cell
• Length breadth and height of the cells approximately equal
• Central spherical nucleus
• Location;
  • glands
  • collecting duct
  • nephron
• function;
  • secretion and conduction of secreted substances

 

Simple columnar epithelium

• Cells are tall
• nucleus found in the basement region
• Goblet cells are dispersed between columnar cells
• Function;
  • secretion
  • absorption
• free surface of the small intestine made up of simple columnar epithelium have microvilli
• extended from stomach to large intestine

 

Ciliated epithelium

• If the surface of epithelial cells have cilia they are known as ciliated epithelium
• Areas at which ciliated epithelium found
  • nasal cavity
  • trachea
  • cerebral ventricle
  • respiratory tract
  • fallopian tube

 

Compound epithelium

• it consists of three different types of epithelial tissues
  • stratified epithelium
  • transitional epithelium
  • pseudo stratified epithelium

 

Stratified epithelium

• cells are arranged in many layers
• the lowermost layer which lie above the basement membrane is known as germinal layer
• they have the ability to divide
• the uppermost layer of cells are squamous epithelial cells
• non keratinized at the areas where moisture is found e.g- oesophagus, buccal cavity and vagina
• cornified at the area where there is no moisture e.g.-epidermis of the skin. They are dead cells found in areas where wear and Tear occur

 

Transitional epithelium

• cells are elastic to certain degree when tension or thrust occur
• found in urinary bladder, urinary tract of male animal and renal pelvis
• function include- elastic thus store a certain amount of urine and sustain the toxicity of urine

 

Pseudostratified epithelium

• two types of cell all of which are line on the basement membrane
• small cells lost the ability to reach the free surface
• large cells form the free surface
• function- mucus secretion
• location- wall of trachea urinary tract bile duct

 

• Pseudostratified ciliated epithelium –                     respiratory tract
• Stratified columnar epithelium –                               cornea and mammary duct
• Stratified squamous epithelium –                             oesophagus
• Pseudostratified ciliated columnar epithelium – respiratory tract

• consists of many types of cells, fibres and large amount of matrix
• mesodermal origin
• supplied with blood vessels and nerves
• functions include
  • structural support
  • physiological connection
  • binding the organs and tissues together
  • protection
  • transport
  • heat insulator

 

Loose connective tissue

• many types of cells dispersed in the matrix
• loosely and randomly arranged fibres
• there are two types of loose connective tissue
  • areolar connective tissue
  • adipose tissue
• Areolar connective tissue
• it is the typical connective tissue
• transparent matrix
• 50% of matrix is made up of glycoprotein
• two types of fibres are found
  • white fibre
  • yellow fibre
• white fibre
• collagen protein
• unbranched
• inelastic
• large cross section
• made up of bundles of fibres
• wave like structure

 

 

• yellow fibre
• elastin protein
• branched
• elastic
• small cross section area
• singly arranged
• straight

 

• areolar connective tissue consists of 5 types of cells
  • fibroblast –              secrete fibre
  • phagocytic cell –              phagocytosis
  • monocyte –              phagocytosis
  • Basel cell –              secrete matrix
  • adipose cell –              fat storage
  • protoplasmic cell – secrete antibiotics
  • lymphocyte –              formation of protoplasmic cell
• intermediate tissues produce other cells
• areolar connective tissue found in much amount in the body
• location – mucosa and submucosa
• function – connect organs and tissues
• Adipose tissue
• the aggregation of adipose cells in the connective tissue leads to the formation of adipose tissue
• location;
  • beneath the skin of mammals
  • heart
  • Mesenteries
  • surrounding the kidney
  • orbital cavity
• function;
  • heat insulator
  • shock absorber
  • energy storage

 

Dense connective tissue

• tightly packed collagen fibres making it stronger than loose connective tissues
• it consists of two types of tissues
  • Dense regular connective tissue
  • Special connective tissue
• Dense regular connective tissue
• The fibres in this tissue are lined up in parallel and they are in an order
  • Tendons bind muscle to bone
  • ligaments bind bone to bone
• This type of connective tissue produce coverings that pack organs e.g.- epimyoeum covers the skeletal muscle, perineurium cover nerves
• Special connective tissue
  • Cartilage
• Cartilage is a special connective tissue in which the ground substance is formed by glycoprotein called chondrin.
• Collagen fibres are laid down along the lines or as parallel rays
• the result is a firm and flexible tissue that does not stretch
• the matrix is deposited by cells called chondroblast
• all chondroblast become enclosed in space called lacuna
• in this enclosed condition they are termed as Chondrocytes
• the margin of the cartilage is covered by a dense layer of cells and fibrils hold the perichondrium
• from the perichondrium new chondroblast are produced and added to the internal matrix
• the matrix is highly elastic and is able to absorb mechanical shock
• there are three types of cartilage
  • Hyaline cartilage (Shining)
• the matrix is semi-transparent
• each lacuna consist 1, 2, 4 or 8 chondrocytes
• g.- C shaped rings in trachea, bronchi and bronchioles embryonic skeleton in bony vertebrates and cartilage fishes such as shark
  • Yellow elastic cartilage
• Elastin protein is dominant
• They are more flexible and Elastic than Hyaline due to the presence of yellow fibres
  • White fibrous cartilage
• Contains large number of bundles of the collagen fibres than hyaline
• This provides greater tensile strength than hyaline. E.g.-in between two vertebrae

 

• • Bone tissue
• Bone is the most abundant tissue in all animal skeletal material
• there are three main functions of bones;
  • support
  • protection
  • metabolic function
• all the cells in the body structure are embedded in a calcified matrix
• About 30% of the matrix is composed of organic materials such as collagen fibres and glycoproteins
• about 70% of the matrix composed of inorganic materials such as calcium hydroxyapatite, sodium, magnesium, Potassium, Chloride, fluoride, Bicarbonate and citrate ions also present invariable amounts
• bone cells called osteoblast are contained in space is called lacuna
  • Compact bones
• A transverse section of a compact bone shows it consists of numerous cylinders called Harvesian system
• Each harvesting system contains a pore called Harvesian canal.
• Each system contains a set of layers called lamella.
• Each odentoblasts are interconnected by fine canals called canaliculi.
• An artery, a vein, a lymphatic vessel and nerve fibre run through each harvesian canal.
• The combination of organic and inorganic materials produce a structure of great strength.
• A bundle of collagen fibres which cover the bone is called periosteum.
• The inner region of the periosteum has blood vessels and the cells that can develop into osteocytes.
  • Blood
• The average adult has about 5 dm³ of blood.
• The cells make up about 45% and the plasma about 55% by volume of the blood
• the pH of the blood is kept at the range of 7.35 – 7.45
  • Plasma
• Plasma is a pale yellow coloured liquid.
• It consists of 90% water and 10% of a variant of substance
• Components of blood plasma and its function
  • Water major constituent of blood and lymph. Transport of many dissolved materials. Regulation of water content.
  • Plasma proteins bind and transport calcium.
  • There are three types of globulins. They are;
    • Alpa globulin
    • Beta globulin
    • Gama globulin
      • Alpha globulin
    • Bind and transport thyroxin, lipids and fat soluble vitamins A, D, E and K
      • Beta globulin
    • Bind and transport fats, cholesterol and fat soluble vitamins
      • Gamma globulin
    • Important in immune response

 

• Prothrombin involve in blood clotting
• Fibrinogen involve in blood clotting
• Enzymes involve in metabolic activities
• Mineral ions example ions of Sodium, Potassium, calcium, magnesium, chlorine, bicarbonate, phosphate and sulphate regulate solute potential and pH level in the blood
  • Blood cells
• Red blood cells.

• In human red blood cells are small cells that lack nuclei when mature.
• They appear as circular by concave disc.
• Their average diameter is 7- 8 micrometre.
• And they are about 2.2 micrometre thick.
• The particular shape results in a large surface area to volume ratio than that of a sphere.
• Each cell is very thin and allows efficient diffusion of gases across its surface.
• There are about 5 million red blood cells in 1mm³ of blood.
• Red blood cell are packed with haemoglobin.
• Haemoglobin is the oxygen carrying protein pigment which gives blood its red colour.
• Haemoglobin combines temporally with oxygen to form oxy haemoglobin in areas of high oxygen concentration. (e.g. lungs) And release the oxygen in the regions of low concentration (e.g. body cells)
• Each red blood cell has a relatively short lifespan of about 120 days.
• All red blood cells get destroyed in spleen or the liver.
• The protein portion of the red blood cells is broken down into amino acids and reused.
• The iron of the Haem is stored in the liver as ferritin and reused later in the production of red blood cells.
• The remaining of the Haem molecule is broken down into Bilirubin and Biliverdin.
  • White blood cells
• These cells are larger than red blood cells and present in much smaller numbers.
• There are about 1000 cells in 1mm³ of blood.
• They play an important role in the body’s defence mechanism against diseases
• Their lifetime in the blood stream is only a few days all are capable of moments known as amoeboid moments
• white blood cells are of two types;
  • granulocytes
  • agranulocytes
• Granulocytes
• These cells are made in bone marrow can be further divided into three

1. neutrophils
2. Eosinophil
3. basophil
4. Neutrophils

• they are actively phagocytic and engulf and digest disease causing bacteria
• 70% of WBC is Neutrophils

2. Eosinophil

• 5% the population
• increases when people are affected with allergic conditions such as asthma

3. Basophil

• 5% of the population
• Secrete anticoagulants histamine and heparin

 

• Agranulocytes
• further divided into two categories

1. Monocyte
2. Lymphocyte

 

1. Monocyte

• These are formed in bone marrow and have kidney shaped nucleus
• They are phagocytic and engulf bacteria and other foreign bodies by endocytosis
• They also play major role in immune system by producing a certain antigens

2. Lymphocyte

• 24% of these are produced in the thymus gland it possesses only a small quantity of cytoplasm
• Two types of Lymphocytes found naturally.
• They are T lymphocytes and B Lymphocytes
• They are involved in immune reactions such as antibody production

Platelets

• platelets are irregular shaped cellular fragments
• usually lack in nuclei
• they are responsible for starting the process of blood clotting
• they survive about 5 to 9 days before being destroyed by the spleen and liver

• The nerve tissue and its cell include neurones and the supporting cells called neuroglia
• neurones are specialised to produce and conduct electrical impulses
• most neurones consists of three parts
  • cell body
  • dendrites
  • axon
• the cell body of a neurone contains a nucleus
• dendrites are highly branched extensions which receive incoming impulses and conduct electrical events to the cell body
• the outgoing impulses produced at the origin of the axon
• the axon is a single extension that conduct impulses away from the cell there are
• three main neurones
  • Sensory neurone located in the skin eyes ears nose
    • Functions- receive information from the body and send impulses to the central nervous system
  • Intermediate neurones located in the brain and spinal cord
    • Functions- integrate information and conduct impulses between sensory neurones and motor neurones
  • Motor neurones located in the muscles and glands, central nervous system end effectors
    • Function- simulate muscles and glands by conducting impulses out of the central nervous system
  • Neuroglia do not conduct electrical impulses but instead support and insulate neurones.
  • In many neurones neuroglia cells associate with their actions and form an insulating covering called myelin sheath
  • myelin sheath serves as sites for accelerating impulses

 

General characters of all types of muscle tissue includes;

1. Extensibility
2. Elasticity.
3. Excitability or irritability.
4. Contractility.

.

• Extensibility
  • The ability to stretch or contract
• Elasticity
  • The ability to return to its original length after being stretched or contracted.
• Excitability or irritability
  • Ability to receive and respond to stimuli
• Contractility
  • Ability to contract or shorten

 

• Muscle cells are of three types
  • smooth muscles
  • skeletal muscles
  • cardiac muscles
• all the muscles can be categorised into two main types
  • striated muscles –              skeletal and cardiac
  • unstriated –              muscles smooth
• Functions of each skeletal muscle is under voluntary control and function of cardiac and smooth muscle is generally involuntary

 

Smooth muscles

• Smooth muscles are the earliest form of muscles in the process of evolution in vertebrates
• smooth muscles occur in the organs of the internal environment as well as on the skin
• smooth muscle tissue is organised as sheets of long spindle shaped cells containing a single nucleus
• in some tissues the cells contract when they are stimulated by enough stimulus and all the cells in the sheet contracts as a unit e.g.- Wall of the blood vessels, intestine, stomach, Iris

 

Cardiac muscles

• The hearts of vertebrates are composed of branched cardiac muscles
• Cardiac muscles are interconnected cells with a single nucleus
• Each muscle fibre contains millions of Mitochondria
• Each fibre is made up of many myofibrils (fibres made of protein)
• The dark band in between two cells are known as intercalated disc
• These bands are regions where neighbouring cells are linked by gap junctions
• They are permitting the movement of substances and electrical charges from one cell to the another
• This interconnections collectively form the cardiac muscle into a single functional unit.
• all cardiac muscles can generate electrical impulses by the collection of Nerve cells, SA nodes and AV nodes
• The rate of impulses are regulated by sympathetic and parasympathetic nervous system

 

Skeletal muscles

• Skeletal muscles are attached by tendons to bones
• When the muscles contract they cause a bone to move at the joints.
• Skeletal muscle is made up of numerous long muscle cells called muscle fibres
• Each skeletal muscle fibre is stimulated by means of substructure called myofibrils containing actin and myosin
• A mature muscle fibre contain many nuclei

 

Skeletal muscle	Smooth muscle	Cardiac muscle
Shape: long ,cylindrical, unbranched ,arranged parallel to each other	Fusiform, unbranched	Short, cylindrical, branched
each muscle fiber(cell) has many nuclei (the nuclei are located near the surface of each fibre )	Uninuclear	Uninuclear
Striated	Non striated	Striated
sarcomere present	sarcomere absent	sarcomere present
Intercalated discs absent	Intercalated discs absent	Intercalated discs present
nerve supply by central – nervous system and Peripheral nervous system	by autonomic nervous system	by autonomic nervous system
Neurogenic	Neurogenic	Myogenic
No rhythmic contraction	Some rhythmic, Others non rhythmic	rhythmic contractions
fatigue easily	fatigue slowly	Do not fatigue
Voluntary	involuntary	involuntary