Chapter 7 Structural Organisation in Animals Part 1 by TEACHING CARE online tuition and coaching classes

Chapter 7 Structural Organisation in Animals Part 1 by TEACHING CARE online tuition and coaching classes

Structural organization in Animals Part 1


Animal Tissues:-


A tissue can be defined as a group of cells similar in structure, origin and function.


The word “tissue” was given by a French anatomist and physiologist Bichat (1771-1802). But the the term tissue had already been coined by N. Grew (1682) in reration to plant anatomy.


An Italian scientist Marcello Malpighi (1628-1694) is “founder of histology“. He founded a separate branch for the study of tissues called histology.


The term ‘histology’ was given by a German histologist Mayer (1819). Histology is also known as microscopic anatomy.

Bichat (1771-1802) is considered as “Father of histology”.


Types of Tissues


Depending upon the location and function, animal tissues are categorised into four types



Type Origin Function
1. Epithelial tissue Ectoderm, endoderm, mesoderm Protection, secretion, absorption etc.
2. Connective tissues Mesoderm Support, binding, storage, protection,
3. Muscular tissue Mesoderm circulation.
4. Nervous tissue Ectoderm Contraction and movement
    Conduction and control



1.  Epithelial Tissue


The cells of the epithelial tissue/epithelium are placed very close to each other, separated by very thin layers of extra cellular material. The neighboring cells are held together by cell junctions. The epithelial tissue rests on a non-cellular Basement Membrane, which separates the epithelial tissue from the underlying connecting tissue.


The basement membrane is a non-cellular membrane composed of two layers.


  1. The upper thin layer called as basal lamina (composed of glycoproteins and mucopolysaccharides secreted by epithelial cells).


  1. Lower thick fibrous layer called as reticular lamina, (composed of reticular fibres and collagen fibres which are parts of the underlying connecting tissue).


Blood vessel are not present in epithelial tissue. Materials are exchanged between epithelial cells and vessels of the connective tissues by diffusion through the basement membrane.


Classification of epithelial tissue:-


Simple Epithelium


It is composed of a single layer of cells. The adjacent cells are held together with the help of desmosome, resting on the basement membrane. Simple epithelium is found mainly on secretory and absorptive surfaces. It helps in nutrition, excretion, secretion but not for protecting the underlying tissue.


  1. Squamous Epithelium It consists of a layer of thin, flat cells with conspicous nuclei. The cells contain irregular boundaries that fit closely into those of neighbouring Squamous epithelium forms the inner lining of lung alveoli and blood vessels (Endothelium) and is also known as pavement membrane and tesselated epithelium.


  1. Cubical Epithelium has cells which have polygonal outline, but appear cuboid in vertical section. It forms the lining of small salivary and pancreatic ducts and thyroid vesicles. It participates in secretion, excretion and The cells of cubical epithelium in absorptive surface often bear Microvilli on their free ends. It gives a brush-like appearance to their free ends. They are,hence, called as Brush-Bordered Cubical Epithelial Cells e.g., in proximal tubules of kidneys. Microvilli increase the area of the free surface of the cell and thereby enhance absorption.


  • Columnar Epithelium is characterised by the presence of tall polygonal columns like cells. The nucleus is mostly located at the base of the cell. Columnar epithelium is present on the inner surface of the intestine, stomach and gall bladder. It is also found in gastric and intestinal glands. The function of columnar epithelium is secretion or absorption. The intestinal mucosa is lined by Brush-Bordered Columnar Epithelium which is highly


  1. Ciliated Epithelium consists of columnar or cubical cells with cilia on their free surfaces. The function of the cilia is to move particles, free cells or mucus in a specific direction over the epithelial surface. Ciliated epithelium is present on the inner surfaces of some hollow visceral organs such as Fallopian tubes, bronchioles and small Ciliated columnar epithelium present in the ventricles of brain and spinal canal is called as ependyma. Cilia is of two types (a) Kinocilia are montile cilia with 9+2 organisation, (b) Stereocilia-Basal granule absent, non-motile, 9+2 organisation is absent. Stereocilia is found in some parts of the male reproductive tracts such as the epididymis and vas deferens.


  1. Pseudostratified Epithelium: It is present on the inner lining of trachea and large bronchi. Though, it consists of a single layer of columnar cells but it appears two-layered, because some cells are shorter than the others with their nuclie at a different level. The shorter cells do not have cilia and secrete mucus which traps particles on the epithelial surface. The longer cells have cilia. The ciliary movements propels the mucus and the particles towards the larynx. Pseudostratified non ciliated columnar epithelium is found in urethra of male and parotid salivary


Compound Epithelium


It is composed of more than one layer of cells. Only the deepest layer cells rest on the basement membrane. Being multilayered, compound epithelia have little role in secretion or absorption, but they provide protection to the underlying tissues against mechanical, chemical, thermal or osmotic stresses. Compound epithelia can be stratified or transitional.


  1. Stratified Epithelium has many layers of epithelial cells. The deepest layer is composed of cuboidal cells. But the morphology of the superficial layers varies in the stratified epithelia. In stratified cuboidal epithelium the superficial cells are cuboidal. It lines the inner surfaces of larger salivary and pancreatic ducts. Stratified non- keratinised Squamous Epithelium lines the moist surfaces such as those of buccal cavity, pharynx and oesophagus. It has many superficial layers of living squamous cells and deeper layers of interlinked polygonal cells. Stratified Keratinised Squamous Epithelium covers the dry surface of skin. It has several superficial layers of horny, scale-like remains of dead squamous cells and several deeper layers of living polygonal Heavy deposits of an insoluble protein, keratin in the dead superficial cells make the epithelium impermeable to water and highly resistant to mechanical abrasions. On the contrary, non keratinised stratified epithelia cannot prevent water loss and afford only moderate protection against abrasions.


  1. Transitional Epithelium It is much thinner and more stretchable than the stratified epithelium. It has a single layer of cuboidal cells at the base, 2-3 middle layers of large polygonal or pear-shaped cells and a superficial layer of large, broad, rectangular or oval cells. It is present on the inner surface of the urinary bladder and It allows for considerable expansion of these organs to accommodate urine, because stretching sufficiently flattens and broadens the cells of superficial and middle layers.


Histologists have identified two more types of epithelia, which can not be included in any of the above types of epithelia.

a .neuroepithelia cell of epithelia origin. These cells are specialized for sensory functions (e.g., cells of taste bud).

b.myoepithelial cell, are branched cells that contain muscle proteins, such as myosin and actin. They are specialized for contraction of the muscle cells of sweat glands, mammary glands and salivary glands.

Glandular Epithelia


  1. The cells of glandular epithelia are usually columnar or cuboidal. The glandular epithelium can be classified into two types :
    1. unicellular, composed of isolated glandular cells (e.g., globlet cell of alimentary canal), and multicellular, composed of cluster of cells. A gland, with a single unbranched duct is called a simple gland. The secretory part of the gland consists of epithelial cells arranged in the form of tubes (tubules) or sacs (acini,

alveoli) or a combination of both. The duct is also composed of epithelial cells. Tubular gland, found in the human intestine, is an example of the simple gland. A gland with a branched system of duct is called a compound gland in which the secretory tubule or acinus may be coiled or branched and opens into the single duct of the gland.

Compound glands are present in the pancreas and sub-mandibular salivary glands.


Types of simple gland


  1. Simple tubular: present in the intestine (e.g., Crypts of Leiberkuhn).


  1. Simple alveolar: Terminal part forms alveolus g., Mucous glands in skin of frog, poison glands in toad.


  1. Simple coiled tubular: Terminal part is coiled g., sweat gland.


  1. Branched tubular: Gastric glands in


  1. Branched alveolar g., Sebaceous gland.


Types of compound gland


  1. Compound saccular gland: g., Salivary glands, (sub-maxillary and sub-lingual).


  1. Compound tubulo alveolar: They are tubular as well as alveolar. They are found in mammary glands, pancreas, parotid salivary gland, Cowper’s glands and Bartholin


  1. Exocrine glands have a secretory portion, which contains the cells for secretion. On the basis of mode of secretion, glands can be classified into
    1. Exocrine glands: They transport their secretions to the respective sites of action, for example, salivary gland, tear gland, gastric gland and intestinal
    2. Endocrine gland: They transport their secretions to the respective sites of action via
    3. Heterocrine gland When a gland performs both exocrine and endocrine functions, it is called a mixed gland

or Heterocrine gland (e.g., the pancreas, testis, ovaries).


  • On the basis of mode of secretion, glands can also be classified as:


  1. Holocrine glands: In holocrine glands, the product of secretion is shed with the whole cell resulting into its destruction. g., sebaceous gland


  1. Merocrine glands: When the secretory granules leave the cell by exocytosis without loss of other


cellular material, the glands are called merocine glands e.g., the Pancreas.


  1. Apocrine glands: In aporcrine glands, only the apical portion of the cytoplasm is discharged along with the secretory e.g. mammary gland and axillary sweat glands.



Specialized Junctions between Epithelial Cells


1.     Tight junctions (= Zonula occludens): Plasma membranes in the apical parts of the adjascent epithelial cells get tightly packed together or even fused to form the tight junctions. They help to prevent leaking of substances across the tissue.

  1. Inter-digitations: They are interfitting, finger like membranes proccesses of the adjascent cells. They increase the surface area of contact between the adjascent cells and hence their

3.     Intercellular Bridges: They are minute projections arising from adjacent cell membranes to make contact with one another.

  1. Gap Junctions: Allow cells to communicate with each other by cytoplasmic connections between adjoining cells, for rapid transfer of ions, small molecules and occasionally big

5.     Intermediate Junctions (= Zonula adherens): They generally occur just below tight junctions. The intercellular space at such places contains a clear, low electron density fluid with a dense plaque like structure on cytoplasmic side of each plasma membrane from which fine microfilaments of actin (protein) extend into the cytoplasm. There are no intercellular


filaments between the adjacent cell membranes. There is an adhesive material at this point. They serve anchoring function.

6.     Desmosomes (= Macula adherens): Help in cementing of neighboring cells together. They are like zonula adherens but thicker and disc like junctions. They have intercellular protein. The plaque-like structures (protein plate) are much thicker. The microfilaments which extend from plaque-like structure into the cytoplasm are not of actin, but of a keratin like proteins. These microfilaments are called tonofirils. Desmosomes serve anchoring function. Hemidesmosomes (single sided desmosomes) are similar to desmosomes, but the thickening of cell membrane is only on one side. Hemidesmosomes join epithelial cells to basal lamina (outer layer of basement membrane).



2. Connective Tissue:



Types of Connective Tissue:



  1. Connective Tissue Proper


  1. Loose – More matrix less fibre g., Adipose Tissue, Areolar Tissue


  1. Dense – More fibres less matrix g., Ligament, Tendon, White fibrous, Yellow fibres
  1. Supportive Connective Tissue: Bone, Cartilage


  1. Fluid Connective tissue g., Blood / Lymph


Types of connective tissue fibers: (released by subunits secreted by fibroblasts)


  • Collagen fibers, the most common fibers in connective tissue proper, are long, straight, and
  • Elastic fibers contain the protein elastin and are branched and wavy, returning to their original length after being stretched.
  • Reticular fibers are the least common of the three, thinner than collagen fibers, forming a branching, interwoven network in various organs.



Connective Tissue Proper:


Connective tissue proper cell types


  • Fibroblasts/ Histiocytes /Clasmatocytes are the most abundant cells responsible for the production and maintenance of the connective tissue fibers and the ground

·         Macrophages are scattered among the fibers which engulf (phagocytize) pathogens or damaged cells encountered in the tissue; responsible for chemicals released that mobilize the immune system into drawing more macrophages into an area.

  • Fat cells are also called adipocytes. A fat cell contains such a large droplet of lipid that the nucleus and other organelles are pushed to one side. The number of cells varies from one tissue type to another, from one region of the body to another, and from one individual to

·         Mast cells are mobile connective tissue cells often found near blood vessels. The cytoplasm is packed with vesicles filled with chemicals that are released to start the body’s defence system when the need arises. Mast cells produce-

Histamine – Inflammatory substance produced during allergic reactions.


Heparin – Natural anti-coagulant.


Serotonin – Vasoconstrictor

  • Phagocytic and antibody-producing WBCs/ cart wheel cells may move throughout the connective tissue increasing their numbers during an


Connective tissue proper types:


  • Loose Connective Tissue: Consists of cells scattered within a amorphous ground substance of proteins, strengthened by a loose scattering of fibres such as collagen, elastin, (which makes tissue elastic) and reticulin, which supports the tissue by forming a



  • Adipose Tissue: It is present beneath the skin, around kidneys, and in mesentery and bone marrow. In addition to, fibroblastss, macrophages, collagen fibres and elastic fibres, the adipose tissue also contains large, spherical or oval cells called Fat Cells or Adipocytes. The cytoplasm and organelles in adipocytes are surpassed by fat into a narrow annular layer just beneath the plasma The adipose tissue synthesises, stores and metabolises fat.


Functions :



  1. Prevention of heat loss by forming a heat insulating layer beneath the


  1. Forms shock absorbing cushions around kidneys and


  • Acts as a food





  • Areolar Tissue: It is present under the epithelia of many hollow visceral organs, skin and in the walls of arteries and The areolar tissue joins different tissues and forms the packing between them and helps to keep the organs in place and in normal shape.
  • Dense Connective Tissue: Fibres and fibroblasts are compactly packed. Orientations of fibres may be a regular or irregular pattern and accordingly called dense regular and dense irregular In the dense regular connective tissues, fibroblasts are present in rows between many parallel bundles of fibres e.g., tendons and ligaments. Dense irregular connective tissue has fibroblasts and fibres (mostly collagen) oriented in different directions. Eg. in the skin, in perimysium, perineurium and bones as periosteum.



  • White Fibrous Tissues : Contains only a few fibroblasts scattered among the dense network of thick collagen bundles. It hashigh tensile eg. found at the joint between skull bones making them immovable.



  • Tendons : It is a very dense, strong and fibrous connective tissue having thick parallel bundles of collagen fibres. A few flat tendon cells


are present in a single rows between the collagen bundles. Tendons join a skeletal muscle to a bone.


  • Ligament : Ligaments join bones to bones at joints and hold them in position. Excessive pulling of ligaments causes sprain. Ligaments are composed of bundles of elastic fibres and few collagen

Mummies still have their arteries intact due to well preserved elastic fibres.



  • Reticular tissue : consists of star-shaped reticular cells whose protoplasmic processes from a net work. They cells are phagocytic. Matrix and other types of cells are also present in spaces of Reticular tissues are present in the spleen, lymph nodes, bone marrow etc.





Supportive connective tissue
  • Cartilage : Cartilage is a solid, semi-rigid flexible connective tissue. Chondrocytes are large cartilage cells occurring in groups of 2 or 3 cells in small spaces (lacunae) in the





  • Hyaline Cartilage: the matrix is apparently fibre-less, glass-like (hyaline) but translucent. It is found in the larynx, nasal septum, tracheal rings and ribs.



  • White fibrous cartilage: contains rows of chondrocytes between thick dense bundles of collagen fibres. It is found at joints between Collagen fibres make such joints strong, but less elastic and only slightly movable



(d)        Yellow elastic fibrocartilage: It contains a dense network of yellow elastin fibres scattered between chondrocytes. It constitutes the Eustachian tube, epiglottis and pinna of ear.



(2) Bone




  • It is a solid, rigid connective tissue whose matrix has deposition of apatite salts of calcium and phosphorus. e.g., hydroxyapatite salts and fluoroapatite



  • About 60-70% of bone is composed of inorganic matter and 30-40% of organic


  • If put in HCL, the bone becomes decalcified, soft and flexible but not in



(iv)       Osteoblast are cells which form bone and secrete ossein protein.



  • Osteocytes are metabolically inactive bone cells present in



  • Bone is a solid, rigid, strong connective tissue whose matrix is heavily deposited with apatite salts of calcium and phosphorus. Flat irregular spaces called Lacunae are found in the solid matrix. Each lacuna has a flat bone cell or A bone cell has irregular shape with long cytoplasmic processes which extend into minute canals (Canaliculi) radiating from each lacuna.



  • Compact Bone constitutes the dense outer layers of all bones and is composed of many parallel, longitudinal, column-like structures called Haversian Systems, cemented to each other. Haversian canals are connected to each other by Volksman canals. In each Haversian system, many concentric layers (Lamellae) of bony matrix encircle a longitudinal central canal (Haversian Canal). Haversian Canal carries blood vessels and nerves. Lacunae containing osteocytes occur in a layer between two



  • Spongy Bone – The ends of long bones are made up of an open lattice of bone called spongy bone. The spaces within have marrow, where most blood cells are produced. Spongy bone has no concentric organisation like the Haversian system. It is composed of a network of many fine irregular bony plates or Trabeculae. Each trabecula consists of many irregularly arranged lamellae with lacunae between them. It has red bone marrow. Spongy bone is also called as cancellous bone and is found in epiphysis i.e. the ends of long


Differences between Bone and Cartilage
S.No. Bone Cartilage
1. Matrix is composed of tough inflexible material, called ossein. Matrix is composed of a firm, but flexible material called chondrin.
2. Matrix is impregnated with salts, chiefly calcium phosphate and carbonate. Matrix is impregnated with calcium salts only in calcified cartilage.
3. Matrix occurs in concentric lamellae. Matrix occurs in homogenous mass.
4. Matrix contains fibres, but these are indistin-guishable. Matrix may contain fibres, which may or may not be distinguishable.
5. Bone cells (osteocytes) lie in lacunae singly. Growth in bone is bidirectional. Cartilage cells (chondrocytes) lie lie singly or in groups of two or four. Growth in cartilage is unidirectional.
6. Osteocytes are irregular and give off branching processes Chondrocytes are oval and devoid of processes.
7. Lacunae send out canaliculi for the processes of bone cells, which extend into these minute canals. Lacunae lack canaculi.
8 There are outer and inner layers of special bone forming cells, the

osteoblasts that produce new osteocytes, which secrete new lamellae of matrix.

Cartilage grows by division of chondroblasts.
9. Bone of surrounded by a tough sheath, called periosteum. Cartilage is surrounded by a farm sheath, called perichondrium.



Types of Bones:



  1. Cartilage bones / Endochondrial / Replacing bones – They are formed by the replacement of cartilage by the bone e.g., humerus, femur vertebrae, girdle bones except clavicle. Chondroclast are cartilage


  1. Membrane / Investing bone / Dermal – e.g., skull bones, clavide. The bones are formed in the dermis of the skin and are invested over the already present cartilage.


  • Sesamoid bones – They are formed by the ossification of the tendon by bone g., Patella


  1. Visceral bones – They are those bones which get detached from the skeleton and come to lie in visceral organs g.,


  1. OS cordis – Present in interventricular septum of heart of


  1. OS falciparum – Palm of


  1. OS penis – Penis or rat and


  1. OS palbebrae – In the eyelids of


  1. OS rostralis – Snout of



Fluid connective tissue (Blood):



The cells of blood are quite distinct from other connective tissue cells, both in structure as well as functions. The extra cellular material in blood is fluid without fibres. Fluids outside the cells are called Extra cellular Fluids (ECF). Viscosity of blood is 2.5 times higher than water.


The extra cellular material in blood is a straw-colored, slightly alkaline (pH 7.4) aqueous fluid called Plasma.


Constituents of blood collectively called the Formed Elements float in the plasma. Formed elements include blood cells and blood platelets. Blood cells are of two types-Erythrocytes and Leukocytes.




The blood plasma has three major classes of proteins viz. serum albumin, serum globulins and fibrinogen. Plasma proteins act as a source of proteins for tissue cells. Albumin and globulins retain water in blood plasma by their osmotic effects. A decrease in plasma proteins leads to filteration out of excessive amount of water from blood to tissues. That is why hands and feet are swollen with accumulated fluid (oedema) in persons suffering from deficiency of proteins in diet. Albumins and globulins also transport several substances such as thyroxin and Fe3+ in combination with them. One class of globulins, called immunoglobulin, act as Antibodies.

Plasma proteins also maintain the blood pH by neutralizing strong acids and bases. Thus, they act as Acid-Base-Buffers.


Plasma is slightly alkaline non living inter-cellular material constituting about 60% part of the blood. It is a pale yellow, transparent and clear fluid.


Composition of Plasma. Plasma constitutes 55-60% of blood volume.


  1. Water – About 90% to 92% of the plasma is Solids constitute about 8% of the plasma.


  1. Minerals Salts – They include chlorides, bicarbonates, sulphates and phosphates of sodium, potassium, calcium, iron and All salts constitute about 0.9% of plasma. Buffer of the blood is sodium bicarbonate.


Bicarbonates and chloride salts of Na, K and Ca are found in blood plasma.  Co, Fe, SO 4 , & HCO3- are also present.


  1. Nutrients – They includes glucose, fatty acids, phospholipids, amino acids, cholesterol, fats, nucleosides, etc. Minerals salts have been given


  1. Plasma proteins – They constitute about 7 to 8% of They mainly include albumin 4.4%, globulin 1.5%, immunoglobulin, prothrombin and fibrinogen 0.3%.


  1. Defence compounds – Immunoglobulin acting as antibodies, some other substances such as lysozyme and proper din (a large protein) are always present in the plasma. They destroy bacteria, viruses and toxic substances entering into the blood from


  1. Excretory substances – They includes ammonia, urea, uric acid, creatinine,


  1. Dissolved gases – Water of plasma contains oxygen, carbon dioxide and nitrogen in dissolved


  1. Anticoagulant – Blood plasma contains a conjugated polysaccharide, the heparin that prevents coagulation of blood inside blood


  1. Hormones – secreted and released in blood by endocrine


  1. Vitamins and Enzymes – Vitamins and enzymes are present in the blood


Functions of Blood plasma – These can be summarized as under (i) transport, (ii) retention of fluid in blood, (iii) maintenance of blood pH, (iv) body immunity, (v) prevention of blood loss, (vi) conducting heat to skin for dissipation and (vii) uniform distribution of heat all over the body.



Blood Glucose


Glucose is mainly absorbed in the small intestine. It is also absorbed in stomach. Excess of glucose is converted into glycogen in the liver and muscles by insulin hormone. Whenever it is required glycogen is converted into glucose by glucagon hormone. Normal blood


glucose level is about 80 – 100 mg per 100 ml of blood 12 hours after a normal meal. Its concentration rises soon after a carbohydrate rich diet. If blood glucose level exceeds 180 mg per 100 ml, it starts coming in urine, a condition called glucosuria. Fasting glucose is 70

– 110 mg/dl*. Glucose PP* is 110 – 140 mg/dl. If it a higher it causes diabetes mellitus (hyperglycemia). If it is less it causes

hypoglycemia (less amount of glucose in blood).



Blood Cholesterol


Cholesterol is quite useful in limited amount. It is used in the synthesis of bio membranes, vitamin D, bile salts and steroid hormones. The normal normal amount of cholesterol is 80 – 180 mg in 100 ml of blood plasma. Cholesterol appears in blood either by intestinal absorption of fats or by synthesis in the liver or by both. Saturated fats such as ghee and butter increase cholesterol level in the blood that may lead to its deposition in the internal wall of the blood vessels like arteries and veins which causes high blood pressure and heart problems.


Functions of Plasma Proteins



  1. Prevention of blood loss – Fibrinogen and prothrombin have a role in blood


  1. Retention of fluid in the blood – Albumin and globulin retain water in blood


  1. Body immunity – Some globulins called immunoglobulin (glycoprotein’s) act as antibodies in blood and tissue
  2. Maintenance of pH – Plasma proteins act as acid-base buffers e. they maintain pH of the blood by neutralizing acids and bases.


  1. Transport of certain materials – Thyroxin hormone bounds to albumin or specific globulin for transport in the


  1. Distribution of heat – Plasma proteins helps in uniform distribution of heat all over the


  1. Enzymes – Some enzymes also occur in the



Blood Cells – Erythrocytes


Erythrocytes (red blood corpuscles or RBC) are the most abundant of the formed elements of blood. The most important characteristic feature Of RBCs is the presence of hemoglobin, the red oxygen carrying pigment. The total number of RBCs per microlitre (1 l = 1mm3

= 10-6) of blood is known as the Total Count of RBC. It is about 5 millions and 4.5 millions in adult man and adult woman respectively. The total count becomes low in anaemia and after profuse bleeding. Abnormal rise in the total count of RBC is called Polycythemia. Anaemia is caused due to the deficiency of folic acid, vitamin B12 and hemoglobin.


The shapes and sizes of RBCs vary in different classes of animals. In fishes, amphibians, reptiles and birds RBCs are usually nucleated, oval and biconvex. In mammals, they are non-nucleated, biconcave and circular. Only camel and llama possess oval red blood corpuscles. Old and worn out RBCs are phagocytosed and destroyed by macrophages. During this process, the pigment part porphyrin of hemoglobin is catabolised to the yellow pigment Bilirubin which is excreted in the bile. The pale yellow colour of plasma is largely due to billirubin.


If a sample of blood added with potassium or sodium oxalate is centrifuged at a high speed in a graduated centrifuge tube (hematocrit tube), the centrifugal force rapidly sediments the RBCs at the bottom of the tube. They get packed into a solid, red, bottom layer, wherease the leukocytes form a thin, buff-coloured layer. From the graduations on the tube, the relative volume of erythrocytes may be read as a percentage of the total blood volume. It is called the Hematocrit Value or Packed Cell Volume. It normally forms 45


percent of the blood volume.


RBC of mammals are circular, biconcave, non-nucleated except in family camelidae. e.g., camel The camel has non-nucleated and oval RBCs. Largest RBCs are found in amphibian whereas smallest RBC are in mammals. In mammals smallest RBC are found in ‘Musk Deer’ Tragulus javanicus (1.5 m). In mammals largest RBC are found in elephant. (9.4 ).


Life Span


Life span in man = 120 days Life span in frogs = 100 days


Count of RBC

In Man = 5 to 5.5 million/Cu. mm In woman = 4.5 million/Cu. mm In embryo = 8.5 million/Cu. mm Daily destruction of RBC = 1%


ESR (Erythrocyte sedimentation rate): is measured by Wintrobe’s method. It is the rate of setting down of RBC and is also estimated by Westegren’s method. ESR is very useful in diagnosis of various diseases like tuberculosis, ESR in men is 0-5 mm/hour and in women it is 0-7 mm/hr in Westegren method.


Haemocytometer: is an instrument used for counting the number of both W.B.C. and R.B.C.


Rouleaux: In resting and slowly flowing blood, the RBCs aggregate to form rouleaux (the RBCs are piled on top of each other). Fibrinogen facilitates rouleaux condition.


Bone marrow: It is the main site for RBC formation.

Structure of RBC of man: Biconcave, non-nucleated bounded by Donnan’s membrane. (plasma membrane of RBC). Haemoglobin is filled in RBC which is vasculatory pigment or respiratory pigment.


Normal range of Hb



Men            15.5 2.5g/dl (dl = deciliter) Women   14.0 2.5g/dl


Infants    16.5 2.5g/dl



Structure of Haemoglobin: Each molecule of haemoglobin has 4 molecules of haem and 1 molecule of globin. They are attached by co- ordinate bond. Haem is protoporphyrin compound and essentially has 4 pyrrole groups joined together and forms ring structure. In Hb Fe is present in (Fe++) Ferrous form. Hb = Haem 5% & Globin 95%. Globin is made up of 4 polypeptide chains.

Practice Test Paper

  1. Cells of the epithelial tissue rest on a basement membrane which is made up of

(a) Monosaccharides (b) Mucopolysaccharides (c) Disaccharides (d) Lipids

  1. The cells of a tissue are similar in


(a) Structure (b) Function (c) Origin (d) Both (a) and (b)

  1. The intercellular matrix is negligible or absent in which of the following tissue


(a) Connective tissue (b) Epithelial tissue (c) Muscular tissue (d) Cardiac tissue

  1. The basement membrane acts as


(a) Plasma membrane (b) Plasmalemma (c) Both (a) and (b) (d) None of these

  1. The filaments arising from desmosomes are called


(a) Tonofibril (b) Tonofilament (c) Both (a) and (b) (d) None of these

  1. Pseudostratified epithelium is always


(a) Single layered (b) Double layered (c) Multilayered (d) Uncertain

  1. Most of the glands of the body are of


(a) Holocrine type (b) Merocrine type (c) Apocrine type (d) None of these

  1. Reproductive cells (germinal epithelium) are made up of which of the following epithelial tissue


(a) Cuboidal (b) Columnar (c) Squamous (d) Sensory

  1. In chordates the peritoneum covers


(a) Heart (b) Skin (c) Kidney (d) Liver

  1. Covering of lungs is called


(a) Pericardium (b) Pleura (c) Peritoneum (d) Serosa

  1. Schneiderian membrane is found in


(a) Nasal passage (b) Trachea (c) Bowman’s capsule (d) Loop of Henle

  1. Cells of squamous epithelium are


(a) Tall with elongated nuclei (b) Cube like (c) Flat and tile like (d) Columnar or cuboidal in shape

  1. Which of the following makes heart wall more thick


(a) Pericardium (b) Epicardium (c) Myocardium (d) Endocardium

  1. Internal surface of large intestine is


(a) Lined by muscular tissue (b) Lined by epithelial tissue (c) Lined by both types of tissue (d) Lines by all four types of tissue

  1. Desmosomes are the feature of


(a) Epithelial tissue (b) Nervous tissue (c) Muscular tissue (d) None of these

  1. Simple epithelium is


(a) One cell thick (b) Two cells thick (c) Two or three cells thick (d) All of these

  1. The cellular layers in epidermis of skin consists of


(a) Glandular cells (b) Columnar cells (c) A squamous stratified cornified epithelium (d) A complex stratified epithelium

  1. Pavement epithelium is another name for


(a) Cuboidal epithelium (b) Ciliated epithelium (c) Simple squamous epithelium (d) Stratified epithelium

  1. Rapid healing of wounds is found in


(a) Epithelial tissue (b) Muscular tissue (c) Connective tissue (d) Nervous tissue



  1. Microvilli are present in


(a) Stratified squamous epithelium (b) Cuboidal epithelium (c) Columnar epithelium (d) Ciliated epithelium






1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
b d b c c a b a d b a c c b a a c c a c