2. Tissues (1)

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Chapter 2. Animal Tissues

Animals are multicellular heterotrophs whose cells lack cell walls. At some point during their

lives, all animals are capable of movement, although not all animals have muscles they use for this. In themost commonly encountered animals, the mobile stage is the adult, although some animals (such as corals

and sponges) have sessile (or nonmobile) adult phases and mobile juvenile forms. Both animal and plant

evolutionary history show the development of multicellularity and the move from water to land (as well

as a secondary adaptation back to water, for example dolphins, whales, duckweed, and elodea).

Animals developed external or internal skeletons to provide support, skin to prevent or lessen

water loss, muscles that allowed them to move in search of food, brains and nervous systems for

integration of stimuli, and internal digestive systems.

Organs in animals are composed of a number of different tissue types. For example, the stomach

has epithelial tissue making linings and secreting gastric juices, connective tissues. Plants are simpler

organisms than animals, having three organ systems and fewer organs than do vertebrate animals. Organs

are composed of tissues, which are in turn composed of cells. Plants have three tissue types: ground,

dermal, and vascular. Animals have four: epithelial, connective, muscle, and bone.

EPITHELIAL TISSUE

Epithelial tissue is made of closely-packed cells arranged in flat sheets. Epithelia form the surface

of the skin and line the various cavities and tubes of the body. The epithelia that form the inner lining of

blood and lymph vessels are called endothelia. The apical surface of epithelial cells is exposed to the

"external environment", the lumen of the organ or the air. The basolateral surface is exposed to the

internal environment (ECF). The entire sheet of epithelial cells is attached to a layer of extracellular

matrix that is called the basement membrane or, better (because it is not a membrane in the biological

sense), the basal lamina. Epithelial tissue covers body surfaces and lines body cavities. Functions include

lining, protecting, and forming glands. Three types of epithelium occur:

Squamous epithelium consists of flattened cells with a centrally located oval or sphericalnucleus. It forms the inner lining of lungs alveoli, heart, blood vessels, lining of eye lens, outer and

inner lining of Bowman’s capsule.

Cuboidal epithelium consists of cube-shaped cells which are as tall as wide with a central

nucleus. They often form microvilli at their free surfaces giving a brush like appearance, hence called brush bordered cuboidal epithelium. They also develop cilia in certain parts of nephrons of kidney

hence called ciliated cuboidal epithelium.

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Fig. 2.1. Types of epithelial tissues on the basis of arrangementof layers.

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Columnar epithelium consists of elongated cells with a basally located nucleus. They also develop

microvilli and cilia like the cuboidal epithelium. In the lining of the epididymis they develop non-

motile stereocilia. They are secretory in nature (glandular) in gastric glands and mucus secreting

(goblet cells) in lining of the gastrointestinal tract.Any epithelium can be simple or stratified. Simple epithelium has only a single cell layer where

every cells on basement membrane. Stratified epithelium has more than one layer of cells and only the

deepest cells rest on the basement membrane. Pseudostratified epithelium is a single layer of cells but

due to difference in the size of the cells they appear at first glance to form two layers.Functions of epithelial cells include:

• Movement of materials in, out or around the body.

•

Protection of the internal environment against the external environment.• Secretion of a product.

Glands can be single epithelial cells, such as the goblet cells that line the intestine. Multicellular

glands include the endocrine glands. Many animals have their skin composed of epithelium. Vertebrates

have keratin in their skin cells to reduce water loss. Many other animals secrete mucus or other materials

from their skin, such as earthworms do.

SIMPLE STRATIFIED PSEUDOSTRATIFIED

1. Squamous (Lining of pleural cavityand Blood vessels)

2. Cuboidal (Bronchioles, Sweatglands)

(i) Brush bordered (PCT)

(ii) Germinal (Testes and Ovary)

(iii)Ciliated (Nephrons)

3. Columnar (Glandular ducts, Gallbladder)

(i) Ciliated (Fallopian tube)

(ii) Stereociliated (Epididymis)

(iii)Sensory (Retina, Tongue, Brain)

1. Stratified Squamous(Buccal cavity, Oesophagus,Cornea, Vagina)

(i) Keratinized (Epidermis

of skin)

(ii) Non-keratinized

(Buccal cavity, Pharynx,Oesophagus)

2. Stratified Cuboidal (Mammary glands)

3. Stratified Columnar (Pharynx, Epiglottis)

1. Ciliated (Trachea,Bronchi, Bronchioles)

2. Pseudostratified withstereocilia (Epididymis,

Urethra)

Table. 2.1. Classification of epithelial tissues.

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Fig. 2.2. (a) Photograph of peripheral portion of the chick blastodisc atabout 33 hours of incubation. Even though there are several layers of cellsvisible, they are all distinct and separate simple squamous epitheliumlayers. (b) CS through small intestine. The tall, vertical cells seen at the topof the tissue are columnar cells (red arrow)- simple columnar epithelium

(the cells at the bottom are connective tissue).

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CONNECTIVE TISSUE

The cells of connective tissue are embedded in a great amount of extracellular material. This matrix is

secreted by the cells. It consists of protein fibers embedded in an amorphous mixture of protein- polysaccharide (proteoglycan) molecules. Fibres in connective tissue can be divided into three types:

collagen fibres,

reticular fibres and

elastic fibres.

1. Collagen fibres are

the dominant fibre

type in most

connective tissues.

The primary function

of collagen fibres is

to add strength to the

connective tissue.2. Reticular fibres are

very delicate and

form fine networksinstead of thick

bundles. They are

usually not visible in

histological sections

but can be

demonstrated by

using special stains.

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Fig. 2.3. Types of fibres in the connective tissues.

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For example, in silver stained sections reticular fibres look like fine, black threads - coarse collagen fibres

appear reddish brown in the same type of preparation.

3. Elastic fibres are coloured in fresh tissues - they are light yellow - but this colouration is only visible if

large amounts of elastic fibres are present in the tissue, for example, in the elastic ligaments of the

vertebral column.Connective

cells are separatedfrom one another by

a non-cellular

matrix. The matrix

may be solid (as in

bone), soft (as in

loose connective

tissue), or liquid (as

in blood). Two

types of connective

tissue are Loose

Connective Tissue

(LCT) and DenseConnective Tissue

(DCT). These two

tissues are

distinguishedaccording to the

relative amounts of

fibres they contain. Dense connective tissues are completely dominated by fibres. They are subdivided

according to the spatial arrangement of the fibres in the tissue.

In dense irregular connective tissue the fibres do not show a clear orientation within the tissue but

instead form a densely woven three-dimensional network. A good example is the dermis of the skin. We

talk about regular dense connective tissue if the fibres run parallel to each other. Good examples of

regular dense connective tissue are tendons, ligaments and the fasciae and aponeuroses of muscles. Loose connective tissue is relatively cell rich, soft and compliant. It is also rich in vessels and

nerves. It is best understood as a kind of generalised connective tissue in which all connective tissue cell

types may occur. Loose connective tissue may occur in some special variants: mucous connective tissue,

reticular connective tissue and adipose tissue. LCT occurs beneath epithelium in skin and many internal

organs, such as lungs, arteries and the urinary bladder. This tissue type also forms a protective layer over

muscle, nerves, and blood vessels.

Connective tissue cells are usually divided into two groups based on their ability to move within

the connective tissue. Fibrocytes (or fibroblasts) and fat cells are fixed cells. Macrophages, monocytes,

lymphocytes, plasma cells, eosinophils and mast cells are wandering cells.

1. Fibrocytes. Fibrocytes are the most common cell type in connective tissues. They are the "true"

connective tissue cells. The cytoplasm of a resting (i.e. inactive) fibrocyte does not contain many

organelles. This situation changes if the fibrocytes are stimulated, for example, by damage to the

surrounding tissue. In this case the fibrocyte is transformed into a fibroblast, which contains large

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Fig. 2.4. Types of dense connective tissues.

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amounts of the

organelles which

are necessary for

the synthesis and

excretion of proteins needed to

repair the tissuedamage. Fibrocytes

do not usually leave

the connective

tissue. They are,

however, able to

perform amoeboid

movement.

2. Reticular cells.Reticular cells are

usually larger than

an averagefibrocyte. They are

the "fibrocytes" of

reticular connective tissue and form a network of reticular fibres, for example, in the lymphoid organs.

Their nuclei are typically large and lightly stained and the cytoplasm may be visible amongst the cells

which are housed within the network of reticular fibres.

3. Adipocytes. Fat cells or adipocytes are fixed cells in loose connective tissue. Their main function is

the storage of lipids. If "well fed" the cytoplasm only forms a very narrow rim around a large central lipid

droplet. The flattened nucleus may be found in a slightly thickened part of this cytoplasmic rim - if it is

present in the section, which may not be the case since the diameter of an adipocyte (up to 100 µm) is

considerable larger than the thickness of typical histological sections. A "starving" adipocyte may contain

multiple small lipid droplets and gradually comes to resemble a fibrocyte.

4. Mast cells.Mast cells are -

like macrophages,

lymphocytes and

eosinophils - in

demand when

something goes

wrong in the

connective tissue.

Quite a few of

them are present inhealthy connective

tissue as they stand

on guard and

monitor the localsituation. The

cytoplasm of mast

cells is filled by

numerous largevesicles. Mast

cells discharge the

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Fig. 2.5. Types of adipose connective tissues.

Fig. 2.6. Wandering cells of the connective tissues.

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contents of these vesicles if they come in contact with antigens, for example, proteins on the surface of an

invading bacterium or, in allergic reactions, in response to antigens found, for example, on the surface of

pollen grains.

MUSCLE TISSUE

Muscle tissue facilitates movement of the animal by contraction of individual muscle cells

(referred to as muscle fibers). Three types of muscle fibers occur in animals are skeletal (striated), smoothand cardiac.

Muscle fibers are multinucleated, with the nuclei located just under the plasma membrane. Most

of the cell is occupied by striated, thread-like myofibrils. Within each myofibril there are dense Z lines. A

sarcomere (or muscle functional unit) extends from Z line to Z line. Each sarcomere has thick and thinfilaments. The thick filaments are made of myosin and occupy the center of each sarcomere. Thin

filaments are made of actin and anchor to the Z line.

1. Skeletal Muscles.These muscles are generally attached to bones and are at work every time, as they are responsible

for moving parts of the body, such as the limbs, trunk, and face, i.e. they are concerned with voluntary

movements of the body. A skeletal muscle is made up of elongated cells called muscle fibres. Contractionof these fibres tend the muscle to move as a whole. Skeletal muscle fibres are grouped into dense bundles

called as fascicles. A group of fascicles bound together by connective tissue to form a functional muscle.

When viewed under a microscope, skeletal muscles appear to have striations (bands or stripes).

This gives skeleton muscle the name of striated muscles. Mostly these muscles are under the control of

the central nervous system (CNS).

Since these are long and slender

in appearance, they are often

called as muscle fibres rather than

muscle cells. Muscle fibres

together with the connective

tissue, blood vessels, and nerves

form a skeletal muscle.

2. Smooth Muscles.These are spindle shaped,

uni-nucleate, non-striated and

intertwined to form a sheet of

smooth muscle tissue. These are

usually not under the voluntary

control and are found in the

internal organs such as stomach,

intestine, walls of blood vessels,

etc. Smooth muscle fibers are

surrounded by connective tissue,

but the connective tissue does notunite to form tendons as it does in

skeletal muscles. Most smooth

muscle cells can contract without

stimulation from the nervous

system. Because most of its

movements cannot be consciously

controlled, smooth muscles are

also referred to as involuntary

muscles.

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Fig. 2.7. Summary of major types of tissues with their locationin the human body.

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3. Cardiac Muscles.These are striated muscles but not under voluntary control. Cardiac muscles are found only inside

the heart and contract without direct stimulation from the nervous system. A bundle of specialized muscle

cells in the upper part of the heart sends electrical signals through cardiac muscle tissue, causing the heartto rhythmically contract and pump blood through the body. The cardiac muscle cell contains one nucleus

which is located near the center so that adjacent cells form branching fibers pass the nerve impulses from

cell to cell.

NERVOUS TISSUE

Nervous tissue functions in the integration of stimulus and control of response to that stimulus.

Nerve cells are called neurons. Each neuron has a cell body, an axon and many dendrites. The axons of

most neurons are covered with a lipid layer known as the myelin sheath. The myelin sheath both

Insulates and speeds up transmission of action potentials through the axon. In the peripheral nervous

system, myelin is produced by Schwann cells, which surround the axon. Gaps (nodes) in the myelin

sheath along the length of the axon are known as the nodes of Ranvier. Neurons transmit nerve

messages. Glial cells are in direct contact with neurons and often surround them.

• Cell body – It is the largest part, contains the nucleus and much of the cytoplasm (area between the

nucleus and the cell membrane). It is responsible for most of the metabolic activity of the cell,

including the generation of ATP and synthesis of protein.

• Dendrites – These are short branch extensions spreading out from the cell body. Dendrites receive

stimulus (action potentials) and carry impulses from the environment or from other neurons and carry

them towards the cell body.

• Axon – It is a long fiber that carries impulses away from the cell body. Each neuron has only one

axon. The axon ends in a series of small swellings called axon terminals.

The neuron is the functional unit of the nervous system. Humans have about 100 billion neurons

in their brain alone! While variable in size and shape, all neurons have three parts. Dendrites receive

information from another cell and transmit the message to the cell body. The cell body contains the

nucleus, mitochondria and other organelles typical of eukaryotic cells. The axon conducts messages awayfrom the cell body.

SKIN

Skin is an organ of the integumentary system made up of multiple layers of epithelial tissues that

guard underlying muscles and organs. As the interface with the surroundings, it plays the most important

role in protecting against pathogens. Its other main functions are insulation and temperature regulation,

sensation and vitamin D and B synthesis. Skin is considered one of the most important parts of the body.

Skin has pigmentation, or melanin, provided by melanocytes, which absorb some of the

potentially dangerous ultraviolet radiation in sunlight. It also contains DNA repair enzymes which help to

reverse UV damage, and people who lack the genes for these enzymes suffer high rates of skin cancer.

One form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing itto spread quickly, and can often be deadly.

Mammalian skin often contains hairs, which in sufficient density is called fur. The hair mainly

serves to augment the insulation the skin provides, but can also serve as a secondary sexual characteristic

or as camouflage.

The skin is often known as the largest organ of the human body. This applies to exterior surface,

as it covers the body, appearing to have the largest surface area of all the organs. Moreover, it applies to

weight, as it weighs more than any single internal organ, accounting for about 15 percent of body weight.

For the average adult human, the skin has a surface area of between 1.5-2.0 square meters, most of it is

between 2-3 mm thick. The average square inch of skin holds 650 sweat glands, 20 blood vessels, 60,000

melanocytes, and more than a thousand nerve endings.

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Skin is composed of three primary layers: the epidermis, which provides waterproofing and

serves as a barrier to infection; the dermis, which serves as a location for the appendages of skin; and the

hypodermis (subcutaneous adipose layer), which is called the basement membrane.

Epidermis.Epidermis is the outermost

layer of the skin. It forms the

waterproof, protective wrap over the

body's surface and is made up of

stratified squamous epithelium with

an underlying basal lamina. The

outermost epidermis consists of

stratified squamous epithelium with

an underlying connective tissue

section, or dermis, and a hypodermis,

or basement membrane. It contains no

blood vessels, and is nourished by

diffusion from the dermis. The main

type of cells which make up theepidermis are keratinocytes,

melanocytes, Langerhans cells and

Merkels cells. Epidermis is divided

into several layers where cells are

formed through mitosis at the

innermost layers. They move up the

strata changing shape and composition

as they differentiate and become filled

with keratin. They eventually reach

the top layer called stratum corneum

and become sloughed off, or desquamated. This process is called keratinization and takes place within

weeks. This keratinized layer of skin is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out, making skin a natural barrier to infection. The outermost layer of

epidermis consists of 25 to 30 layers of dead cells. Epidermis is divided into the following 5 sublayers or

strata:

Stratum corneum

Stratum lucidum

Stratum granulosum

Stratum spinosum

Stratum germinativum (also called

"stratum basale")

Dermis.The dermis is the layer of skin beneath the

epidermis that consists of connective tissue and

cushions the body from stress and strain. The

dermis is tightly connected to the epidermis by a basement membrane. It also harbors many nerve

endings that provide the sense of touch and heat. It

contains the hair follicles, sweat glands, sebaceous

glands, apocrine glands and blood vessels. The

blood vessels in the dermis provide nourishment

and waste removal to its own cells as well as the

Stratum basale of the epidermis. The dermis is structurally divided into two areas: a superficial area

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Fig. 2.8. Section of skin showing the position of layers andglands.

Fig. 2.9. Enlarged view of epidermis showingthe location of melanocytes.

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adjacent to the epidermis, called the papillary region, and a deep thicker area known as the reticular

region.

(a) Papillary region. The papillary region is composed of loose areolar connective tissue. It is named

for its fingerlike projections called papillae, which extend toward the epidermis. Dermal papillae containcapillaries, bare nerve endings, Meissner corpuscles and Merkel discs. The papillae provide the dermis

with a “bumpy” surface that interdigitates with the epidermis, strengthening the connection between the

two layers of skin. In the palms, fingers, soles, and toes, the influence of the papillae projecting into the

epidermis forms contours in the skin's surface. These are called friction ridges, because they help the hand

or foot to grasp by increasing friction. Friction ridges occur in patterns (see fingerprint) that are

genetically determined and are therefore unique to the individual, making it possible to use fingerprints or

footprints as a means of identification.

(b) Reticular region. The reticular region lies deep in the papillary region and is usually much thicker.

It is composed of dense irregular connective tissue, and receives its name from the dense concentration of

collagenous, elastic, and reticular fibers that weave throughout it. These protein fibers give the dermis its

properties of strength, extensibility, and elasticity. Located within the reticular region are also the roots of

the hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels. Tattoo ink is injected into the

dermis. Stretch marks from pregnancy are also located in the dermis.The hypodermis is not part of the skin, and lies below the dermis. Its purpose is to attach the skin

to underlying bone and issue and elastin as well as supplying it with blood vessels and nerves. It consists

of loose connective tissue and elastin.. The main cell types are fibroblasts, macrophages and adipocytes

(the hypodermis contains 50% of body fat). Fat serves as padding and insulation for the body.

Microorganisms like Staphylococcus epidermidis colonize the skin surface. These microorganisms

serve as ecoorgan. The density of skin flora depends on region of the skin. The disinfected skin surface

gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital

openings.

Functions of Skin.

1. Protection: Skin is an anatomical barrier between the internal and external environment in bodily

defense; Langerhans cells in the skin are part of the adaptive immune system2. Sensation: Skin contains a variety of nerve endings that react to heat, cold, touch, pressure,

vibration, and tissue injury; see somatosensory system and touch.

3. Heat regulation: The skin contains a blood supply far greater than its requirements which allows

precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase

perfusion and heat loss while constricted vessels greatly reduce cutaneous blood flow and conserve

heat. Erector pili muscles are significant in animals.

4. Control of evaporation: The skin provides a relatively dry and impermeable barrier to fluid loss.

Loss of this function contributes to the massive fluid loss in burns.

5. Aesthetics and communication: Others see our skin and can assess our mood, physical state and

attractiveness.

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Skin Glands

Sudoriferous glands: Secrete sweat.Sebaceous glands: Secrete oily material, the sebum which keeps the hair and skin smooth, soft,supple and water-proof.Mammary gland: Modified apocrine sweat glands, functional in females only and secrete milk.Meibomian glands: Also called tarsal glands. These add a film of oil over the cornea.Zeis glands: Pours oily substance in the follicles of eyelashes.Ceruminous glands: Secrete ear-wax or cerumen into the ear canal.Perineal glands: Also called as scent glands. They are present around the genital organs andsecrete pheromones.

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6. Storage and synthesis: Skin acts as a storage centre for lipids and water, as well as a means of

synthesis of vitamin D and B by action of UV on certain parts of the skin. This synthesis is linked to

pigmentation, with darker skin producing more vitamin B than D, and vice versa.

7. Excretion: The concentration of urea is 1/130th that of urine. Excretion by sweating is at most a

secondary function to temperature regulation.

8. Absorption: Oxygen, nitrogen and carbon dioxide can diffuse into the epidermis in small

amounts, some animals using their skin for their sole respiration organ. In addition, medicine can be

administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patchor iontophoresis. The skin is an important site of transport in many other organisms.

COMPETITION DESK # 02

1. The gland cells and nerve plexus lie

(a) in between outer and inner epithelial

layer

(b) in the outer epithelial layers(c) in the inner epithelial layers

(d) amidst ectodermal cells

2. Human skin has a keratinized and water-

impermeable layer of flattened cells. This is

called stratum(a) lucidum (b) corneum

(c) malpighi (d) granulosum

3. The epidermis of mammals is characterized

by the absence of

(a) mucous glands (b) femoral glands(c) poison glands (d) all of these

4. Basic unit of muscle contraction is

(a) actin (b) myosin

(c) sarcomere (d) tropomyosin

5. The base of the placoid scale is attached to

stratum compactum by

(a) subcutaneous fibres

(b) laxum fibres

(c) Sharpey’s fibres

(d) fibres of stratum Malpighi

6. Cells of peritoneum comprise

(a) ciliated epithelium

(b) columnar epithelium

(c) glandular epithelium

(d) squamous epithelium

7. Endothelium lining a blood vessel is formed

of

(a) ciliated epithelium

(b) columnar epithelium

(c) cuboidal epithelium

(d) simple squamous epithelium

8. When a person is exposed to coldsurrounding which of the following does not

occur?

(a) Secretion of adrenal medulla and thyroid

increase

(b) Shivering occurs

(c) Vasoconstriction in skin vessels

supplying blood to hairs

(d) Heart beat and volume of blood per

stroke increases

9. The term blubber refers to

(a) a substitute for natural rubber (b) a subcutaneous deposition of fat in

whale

(c) none of these

(d) the irregular heart beat sounds

10. Tendons and ligaments belong to

(a) muscular tissue

(b) epithelial tissue

(c) fibrous connective tissue

(d) areolar connective tissue

11. Mast cells secrete(a) serotonin (b) heparin

(c) histamine (d) all of these

12. A tissue in which matrix is the source of

structural and functional performance is

(a) muscular (b) epithelial

(c) connective (d) nervous

13. Which of the following are dermal in origin?

(a) sebaceous glands

(b) mammary glands

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(c) Piscean glands

(d) none of these

14. Which of the following muscles are

responsible for moving and shaking of theskin?

(a) arrector pili(b) collagen fibres

(c) Paniculus carnosus

(d) sphincter muscles

15. The surface of skin that is heavily used

becomes thicker and tougher and is full of

(a) eledin (b) keratohyalin

(c) keratin (d) albumin

16. Derivative of sweat gland is

(a) Moll’s gland (b) scent glands

(c) sebaceous glands(d) mammary glands

17. Proprio receptors respond to

(a) mechanical stimuli

(b) chemical stimuli(c) odour

(d) none of the above

18. Which of the following layer is the

outermost one of the skin with dead cells?

(a) Stratum lucidum

(b) Stratum corneum

(c) Stratum spinosum(d) Stratum granulosum

19. Stratum corneum is

(a) dead mid-dermal layer

(b) dead and innermost dermal layer

(c) dead outermost epidermal layer (d) outermost dermal layer

20. Stratum lucidum accumulates a shining

substance called(a) luciferin (b) cardiolipin

(c) cerumen (d) eleiden

21. In mammals melanocytes give protection

from (CBSE 2002)

(a) UV rays (b) Infrared rays

(c) X-rays (d) visible light

22. One of the following is scent gland of

mammals (CBSE 2000)

(a) Bartholin (b) anal

(c) prostate (d) adrenal

23. Pacinian corpuscles occur in the skin of

certain parts of body in mammals. These are

(AIIMS 1998)

(a) type of glands

(b) pain receptors(c) naked tactile receptors

(d) encapsulated pressure receptors

24. Sweat glands, in human skin, are located in

the (AIIMS 1996)

(a) dermis of skin

(b) glandular layer of epidermis

(c) malpighian layer of epidermis

(d) subdermal layer of fat cells.

25. The horns of Rhinoceros are composed of

(AIIMS 1996)

(a) bone (b) cartilage

(c) chitin (d) keratin

26. Camouflage of Chameleon is associated

with (AIIMS 1995)

(a) chromosome (b) chromomere(c) chromoplast (d) chromatopore

27. Which of the following layer of epidermis in

man provides the main protection of body

against water loss and the entry of disease

causing organisms? (AIIMS 1994)

(a) Stratum spongiosum

(b) Stratum corneum(c) Stratum lucidium

(d) Stratum germinativum

28. The colour of the skin is due to (AFMC

2001)

(a) neutrophils (b) mesophils(c) melanocytes (d) basophils

29. The receptors for touch superficially present

in the skin are called (BHU 1997)

(a) Pacinian corpuscles

(b) Krause’s end bulbs(c) Meissner’s corpuscles

(d) Stratum lucidium.

30. The deeper layer of the skin of vertebrates is

called (BHU 1996)

(a) dermis (b) cutaneous tissue

(c) epidermis (d) none of these.

31. Stratum lucidum is found in (BHU 1995)

(a) dermis and they release keratin

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(b) epidermis and situated below the

stratum corneum

(c) dermis and secrete keratin

(d) epidermis and originates from hair

follicle.

32. Epidermis is specialized for (CPMT 1998)(a) respiration (b) absorption

(c) protection (d) all of these

33. One of the following is an example of

cutaneous glands (CPMT 1998)

(a) Gastric (b) Pancreas

(c) Sebaceous (d) Salivary

34. Exposed surface of the human body is

covered by the tissue (CPMT 1998)

(a) glandular epithelium

(b) keratinized stratified squamousepithelium

(c) ciliated epithelium

(d) dermis

35. Inner lining of gut, stomach and liver is

made up of (CPMT 1997)

(a) simple squamous epithelium

(b) simple columnar epithelium

(c) simple cuboidal epithelium

(d) all of these

36. Which of these is not an animal tissue?(a) connective (b) xylem

(c) epithelial (d) nervous

37. Tissues are made up of

(a) groups of cells that perform a different

set of functions

(b) collections of cells that perform similar

or related functions

(c) subcellular structures that aid in the

performance of the cell’s role

(d) none of these

38. Which of these is not a function of epithelial

tissue?

(a) covering surfaces

(b) secretion

(c) support of the body(d) lining internal exchange areas

39. Layered epithelial tissue is referred to as

which of these?

(a) squamous (b) stratified

(c) voluntary (d) pseudostratified

40. Which of these cell types covers the inside

of the mouth?

(a) squamous epithelium(b) cartilage(c) blood (d) cuboidal epithelium

41. Protection of the body from infectious

organisms is accomplished by which of

these tissues?

(a) bone (b) muscle

(c) nerve (d) blood

42. Linking of bone to bone in a skeletal system

is accomplished by which of these tissues?

(a) epithelial (b) connective

(c) muscle (d) nervous

43. Cells that line the tubules in the kidneymake up which of these tissues?

(a) adipose

(b) squamous epithelium

(c) cuboidal epithelium(d) stratified epithelium

44. The storage of fat is accomplished by which

of these cell types?

(a) adipose

(b) squamous epithelium

(c) cuboidal epithelium

(d) stratified epithelium

45. Glands are composed of which of these

tissue types?

(a) epithelium (b) connective

(c) muscle (d) nervous

46. Hard parts of the body would be made of

which of these cell/tissue types?

(a) blood (b) bone

(c) muscle (d) nerves

47. Bone acts as a reservoir for which of theseelements?

(a) carbon (b) nitrogen

(c) calcium (d) hydrogen

48. The blood cells that transport oxygen within

the body are

(a) macrophages (b) erythrocytes

(c) platelets (d) leukocytes

49. Contraction of your heart is accomplished

by which of these cell types?

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7/31/2019 2. Tissues (1)


(a) cardiac (b) skeletal

(c) smooth (d) both a and b

50. Contractions of the uterus during birth are

accomplished by which of these cell types?

(a) cardiac (b) skeletal

(c) smooth (d) both b and c

ANSWERS # 02

1. a 2. b 3. d 4. c 5. c 6. d 7. d 8. d 9. b 10.c11. d 12. c 13. c 14. c 15. c 16. d 17. a 18. b 19. c 20. d21. a 22. b 23. d 24. a 25. d 26. d 27. b 28. c 29. c 30. a31. b 32. d 33. c 34. b 35. b 36. b 37. b 38. c 39. d 40. a41. d 42. b 43. c 44. a 45. a 46. b 47. c 48. b 49. a 50. c

EXPLANATION # 02

2. (b) The outermost cells of stratum lucidum forms a thick layer of hard scale-like, fully keratinized,

flattened cells called stratum corneum. It contains hard keratin filaments (horny cells) which prevents

the passage of water and solutes. In places of friction this layer becomes very thick.

9. (b) In whales and seals the fat of skin forms a thick layer called blubber which is not only reserve food

but also maintains the body temperature.

20. (d) In stratum lucidum, keratohyaline granules are dissolved and transformed into eleiden whichmakes cells semitransparent, shiny and waterproof. It is found in places of friction, such as soles and

palms.

23. (d) Pacinian corpuscles are located in deep layers of dermis of skin, joints, tendons and muscles. Theyrespond to strong pressure and also to vibrations.

29. (c) Meissner’s corpuscles are located in the papillary layer of the dermis just below the epidermis, e.g.

finger tip, lips and nipples. They respond to touch.

33. (c) Sebaceous glands are associated with hair follicles. These secrete oil or sebum which keeps the

hair and skin smooth, soft, supple and water-proof. Emotional stress may increase the secretion of

sebum.

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