Tissues

TISSUES
By Gladys Stephen M.Pharm

TISSUES
A tissue is a group of cells that usually have
a common embryonic origin and function
together to carry out specialized activities.
Tissues may be hard (bone), semisolid (fat),
or even liquid (blood) in their consistency
The tissues in the human body contribute to
homeostasis by providing diverse functions
including
protection,
support
Communication among cells, and
resistance to disease By Gladys Stephen M.Pharm

TYPES OF TISSUES
Body tissues can be classified into four
basic types according to structure and
function:
Epithelial tissue
Connective tissue
Muscular tissue
Nervous tissue

 Epithelial tissue:
 Covers body surfaces and lines hollow organs, body
cavities, and ducts. It also forms glands.
 Connective tissue:
 Protects and supports the body and its organs. Various
types of connective tissue bind organs together, store
energy reserves as fat, and help provide immunity to
disease-causing organisms.
 Muscular tissue:
 Generates the physical force needed to make body
structures move and generates body heat.
 Nervous tissue:
 Detects changes in a variety of conditions inside and
outside the body and responds by generating action
potentials (nerve impulses) that activate muscular
contractions and glandular secretions.

CELL JUNCTIONS
Most epithelial cells and some muscle
and nerve cells are tightly joined into
functional units. Cell junctions are
contact points between the plasma
membranes of tissue cells.
five main types of cell junctions are
Tight junctions
Adherens junctions
Desmosomes
Hemidesmosomes
Gap junctions

Epithelial Tissue
 Consists of cells arranged in continuous sheets, in either single or
multiple layers.
 The cells are closely packed and are held tightly together by
many cell junctions, there is little intercellular space between
adjacent plasma membranes.
 Epithelial tissue forms coverings and linings throughout the body.
It is never covered by another tissue, so it always has a free
surface.
 Epithelial tissues have three major functions:
 Selective barriers that limit or aid the transfer of
substances into and out of the body;
 Secretory surfaces that release products produced by the
cells onto their free surfaces; and
 Protective surfaces that resist the abrasive influences of
the environment.

Apical (free) Lateral surfaces
surface
Epithelium
Basal
lamina
Connective
tissue
Basement
membraneReticular
lamina
Basal surface
Nerve
Blood vessel

 The basement membrane is a thin extracellular layer
consists of two layers
basal lamina and
Reticular lamina
 The basal lamina (lamina thin layer) is closer to—and
secreted by—the epithelial cells
 It contains proteins such as laminin and collagen, as
well as glycoproteins and proteoglycans.
 Laminin molecules adhere to integrins in
hemidesmosomes and thus attach epithelial cells to
the basement membrane.
 The reticular lamina is closer to the underlying
connective tissue and contains proteins such as
collagen produced by connective tissue cells called
fibroblasts

 Epithelial tissue has its own nerve supply, but is
avascular.
 The blood vessels that bring in nutrients and
remove wastes are located in the adjacent
connective tissue.
 Exchange of substances between epithelium and
connective tissue occurs by diffusion.
 Epithelial tissue plays many different roles in the
body; the most important are protection, filtration,
secretion, absorption, and excretion.
 In addition, epithelial tissue combines with nervous
tissue to form special organs for smell, hearing,
vision, and touch.

 Epithelial tissue may be divided into two types.
Covering and lining epithelium
forms the outer covering of the skin and some
internal organs. It also forms the inner lining of blood
vessels, ducts, and body cavities, and the interior of
the respiratory, digestive, urinary, and reproductive
systems.
Glandular epithelium
makes up the secreting portion of glands
such as the thyroid gland, adrenal glands,
and sweat glands.
Endocrine gland
Exocrine gland

Covering and Lining Epithelium
 Classified according to two characteristics:
arrangement of cells into layers
shapes of the cells
 Arrangement of cells into layers
 Simple epithelium
 Pseudostratified epithelium
 Stratified epithelium
 Based on the shapes of the cells
Squamous cells
Cuboidal cells
Columnar cells
Transitional cells

Simple Pseudostratified Stratified
Squamous Cuboidal
Columnar
Cell shape
Arrangement
of layers

 Types of covering and lining epithelia are as follows:
 I. Simple epithelium
A. Simple squamous epithelium
B. Simple cuboidal epithelium
C. Simple columnar epithelium (nonciliated and ciliated)
D. Pseudostratified columnar epithelium (nonciliated and
ciliated)
 II. Stratified epithelium
A. Stratified squamous epithelium (keratinized and
nonkeratinized)*
B. Stratified cuboidal epithelium*
C. Stratified columnar epithelium*
D. Transitional epithelium

Simple Squamous Epithelium
Description:
Single layer of flat cells; centrally located nucleus.
Location:
Lines heart, blood vessels, lymphatic vessels, air
sacs of lungs, glomerular (Bowman’s) capsule of
kidneys, and inner surface of the tympanic
membrane (eardrum); forms epithelial layer of
serous membranes, such as the peritoneum,
pericardium, and pleura.
Function:
Filtration, diffusion, osmosis, and secretion in
serous membranes.

Peritoneum
Nucleus of simple
squamous cell
Cytoplasm
Plasma membrane
Surface view of simple squamous epithelium
of mesothelial lining of peritoneum
Small
intestine
Flat nucleus of
simple
squamous cell
Connective
tissue
Muscular tissue
Simple squamous
cell
Basement membrane
Connective tissue

Simple Cuboidal Epithelium
Description:
 Single layer of cube-shaped cells; centrally located
nucleus.
Location:
 Covers surface of ovary, lines anterior surface of capsule
of the lens of the eye, forms the pigmented epithelium at
the posterior surface of the eye, lines kidney tubules and
smaller ducts of many glands, and makes up the secreting
portion of some glands such as the thyroid gland and the
ducts of some glands such as the pancreas.
Function:
 Secretion and absorption.

Sectional view of simple cuboidal epithelium
of intralobular duct of pancreas
Pancreas
Duodenum
Connective
tissue
Nucleus of simple
cuboidal cell
Lumen
of duct
Simple
cuboidal
epithelium
Simple cuboidal epithelium
Connective
tissue
Basement
membrane
Simple
cuboidal cell

Nonciliated Simple Columnar Epithelium
 Description:
 Single layer of nonciliated column-like cells with nuclei
near base of cells; contains goblet cells and cells with
microvilli in some locations.
 Location:
 Lines the gastrointestinal tract (from the stomach to the
anus), ducts of many glands, and gallbladder.
 Function:
 Secretion and absorption.

Small
intestine
Mucus in
goblet cell
Sectional view of nonciliated simple columnar
epithelium of lining of jejunum of small intestine
Nucleus of
goblet cell
Basement
membrane
Nonciliated
simple
columnar
epithelium
Nonciliated simple
Columnar epithelium

Ciliated Simple Columnar Epithelium
 Description:
 Single layer of ciliated column-like cells with nuclei
near base; contains goblet cells in some locations.
 Location:
 Lines some bronchioles (small tubes) of respiratory
tract, uterine (fallopian) tubes, uterus, efferent
ducts of the testes, some paranasal sinuses,
central canal of spinal cord, and ventricles of the
brain.
 Function:
 Moves mucus and other substances by ciliary
action.

Cilia
Mucus in
goblet cell
Basement
membrane
Connective
tissue
Ciliated simple columnar epithelium
Uterine tube

Pseudostratified columnar epithelium
 Description:
Not a true stratified tissue; nuclei of cells are at
different levels; all cells are attached to basement
membrane, but not all reach the apical surface.
 Location:
Pseudostratified ciliated columnar epithelium lines
the airways of most of upper respiratory tract;
pseudostratified nonciliated columnar epithelium
lines larger ducts of many glands, epididymis,
and part of male urethra.
 Function:
Secretion and movement of mucus by ciliary action.

Trachea
Pseudostratified ciliated columnar
epithelium Ciliated columnar cell
Pseudostratified
ciliated columnar
epithelium
Cilia
Mucus in
goblet cell

Stratified squamous epithelium
Description:
Several layers of cells; cuboidal to columnar shape in
deep layers; squamous cells form the apical layer
and several layers deep to it; cells from the basal
layer replace surface cells as they are lost.
Location:
Keratinized variety forms superficial layer of skin;
nonkeratinized variety lines wet surfaces, such as
lining of the mouth, esophagus, part of larynx, part of
pharynx, and vagina, and covers the tongue.
Function:
Protection.

Vagina
Flattened
squamous
cell at apical
surface
Stratified squamous epithelium
Basement
membrane
Connective
tissue

Stratified cuboidal epithelium
Description:
Two or more layers of cells in which the cells in the
apical layer are cube-shaped.
Location:
Ducts of adult sweat glands and esophageal
glands and part of male urethra.
Function:
Protection and limited secretion and absorption.

Esophagus
Stratified cuboidal epithelium
Stratified cuboidal
epithelium

Stratified columnar Epithelium
Description:
Several layers of irregularly shaped cells; only
the apical layer has columnar cells.
Location:
Lines part of urethra, large excretory ducts of
some glands, such as esophageal glands,
small areas in anal mucous membrane, and
part of the conjunctiva of the eye.
Function:
Protection and secretion.

Stratified columnar epithelium
Esophagus
Stratified
columnar
epithelium

Transitional Epithelium
Description:
Appearance is variable (transitional); shape of
cells in apical layer ranges from squamous (when
stretched) to cuboidal (when relaxed).
Location:
Lines urinary bladder and portions of ureters and
urethra.
Function:
Permits distension.

Urinary bladder
Relaxed transitional epithelium
Transitional
epithelium

Glandular Epithelium
 The function of glandular epithelium is secretion,
which is accomplished by glandular cells that often
lie in clusters deep to the covering and lining
epithelium.
 A gland may consist of a single cell or a group of
cells that secrete substances into ducts (tubes),
onto a surface, or into the blood.
 All glands are classified into
Endocrine glands
Exocrine glands

Endocrine Glands
Description:
Secretory products (hormones) diffuse into blood
after passing through interstitial fluid.
Location:
Examples include pituitary gland at base of brain,
pineal gland in brain, thyroid and parathyroid glands
near larynx (voice box), adrenal glands superior to
kidneys, pancreas near stomach, ovaries in pelvic
cavity, testes in scrotum, and thymus in thoracic
cavity.
Function:
Produce hormones that regulate various body
activities.

Thyroid
gland
Endocrine gland (thyroid gland)
Hormone-
producing
(epithelial) cell
Stored precursor
of hormone

Exocrine Glands
Description:
Secretory products released into ducts.
Location:
Sweat, oil, and earwax glands of the skin; digestive
glands such as salivary glands, which secrete into
mouth cavity, and pancreas, which secretes into
the small intestine.
Function:
Produce substances such as sweat, oil, earwax,
saliva, or digestive enzymes.

Exocrine gland (sweat gland) Skin
Skin
Lumen of duct
of sweat gland
Basement
membrane
Nucleus of
secretory
cell of
sweat gland
Secretory
portion of
sweat gland

CONNECTIVE TISSUE
 most abundant and widely distributed tissues in the
body.
 has a variety of functions.
It binds together, supports, and strengthens other
body tissues;
protects and insulates internal organs;
compartmentalizes structures such as skeletal
muscles;
serves as the major transport system within the
body (blood, a fluid connective tissue);
is the primary location of stored energy reserves
(adipose, or fat, tissue); and
is the main source of immune responses.

General Features of Connective Tissue
 Consists of two basic elements:
Extracellular matrix and cells
 Extracellular matrix is the material located between its
widely spaced cells.
 It consists of protein fibers and ground substance, the
material between the cells and the fibers.
 It is secreted by the connective tissue cells and determines
the tissue’s qualities.
 E.g. in cartilage, the extracellular matrix is firm but pliable.
But the extracellular matrix of bone, by contrast, is hard
and inflexible.
 Do not usually occur on body surfaces, are highly
vascular.

Connective Tissue Cells
The types of connective tissue cells
are
Fibroblasts
Adipocytes
Mast cells
White blood cells
Macrophages
Plasma cells

Reticular
fiber
Fibroblast Eosinophil Mast cell
Neutrophil
Plasma cell
Adipocyte Blood vessel Ground
substance
Elastic
fiber
Collagen
fiber
Macrophage

Extracellular Matrix
 The extracellular matrix consists of two major
components:
(1) ground substance
(2) fibers.
 Ground substance is the component of a connective
tissue between the cells and fibers.
 It may be fluid, semifluid, gelatinous, or calcified.
 supports cells, binds them together, stores water, and
provides a medium through which substances are
exchanged between the blood and cells.
 It plays an active role in how tissues develop,
migrate, proliferate, and change shape, and in how
they carry out their metabolic functions.

FIBERS
Three types of fibers are embedded in
the extracellular matrix between the
cells:
Collagen fibers
Elastic fibers
Reticular fibers

Classification of Connective
Tissues
I. Embryonic connective tissue
A. Mesenchyme
B. Mucous connective tissue
II. Mature connective tissue
A. Loose connective tissue
1. Areolar connective tissue
2. Adipose tissue
3. Reticular connective tissue
B. Dense connective tissue
1. Dense regular connective tissue
2. Dense irregular connective

C. Cartilage
1. Hyaline cartilage
2. Fibrocartilage
3. Elastic cartilage
D. Bone tissue
E. Liquid connective tissue
1. Blood tissue
2. Lymph

Embryonic connective tissue
Embryo
Sectional view of mesenchyme
(connecting tissue)
Ground
substance
Nucleus of
mesenchymal
cell
Reticular
fiber

Mucous connective tissue
Umbilical Cord
Foetus
Mucous connective tissueBy Gladys Stephen M.Pharm

CARTILAGE
Hyaline Cartilage
 Description:
Consists of a bluish-white, shiny ground substance
with thin, fine collagen fibers and many
chondrocytes; most abundant type of cartilage.
 Location:
 Ends of long bones, anterior ends of ribs, nose,
parts of larynx, trachea, bronchi, bronchial tubes,
and embryonic and fetal skeleton.
 Function:
Provides smooth surfaces for movement at joints, as
well as flexibility and support.

Foetus Sectional view of hyaline cartilage of a
developing foetal bone and details of
several chondrocytes
skeleton

Fibrocartilage
Description:
Consists of chondrocytes scattered among thick
bundles of collagen fibers within the extracellular
matrix.
Location:
Pubic symphysis (point where hip bones join
anteriorly), intervertebral discs (discs between
vertebrae), menisci (cartilage pads) of knee,
and portions of tendons that insert into
cartilage.
Function:
Support and fusion.

Portion of
right lower limb
Sectional view of fibrocartilage of tendon
Tendon of
quadriceps
femoris muscle

Elastic cartilage
Description:
Consists of chondrocytes located in a
threadlike network of elastic fibers within the
extracellular matrix.
Location:
 Lid on top of larynx (epiglottis), part of
external ear (auricle), and auditory
(eustachian) tubes.
Function:
Gives support and maintains shape.

ELASTIC CARTILAGE
Auricle of ear Sectional view of elastic cartilage of
auricle of ear

BONE TISSUE
Compact Bone
 Description:
Compact bone tissue consists of osteons (haversian
systems) that contain lamellae, lacunae, osteocytes,
canaliculi, and central (haversian) canals. By contrast,
spongy bone tissue (see Figure 6.3 on page 180)
consists of thin columns called trabeculae; spaces
between trabeculae are filled with red bone marrow.
 Location:
Both compact and spongy bone tissue make up the
various parts of bones of the body.
 Function:
Support, protection, storage; houses blood-forming
tissue; serves as levers that act with muscle tissue to
enable movement. By Gladys Stephen M.Pharm

Femur
Details of an osteocyte

LIQUID CONNECTIVE TISSUE
Blood
 Description:
 Consists of blood plasma and formed elements: red blood cells
(erythrocytes), white blood cells (leukocytes), and platelets
(thrombocytes).
 Location:
 Within blood vessels (arteries, arterioles, capillaries, venules,
and veins) and within the chambers of the heart.
 Function:
 Red blood cells transport oxygen and some carbon dioxide;
white blood cells carry on phagocytosis and are involved in
allergic reactions and immune system responses; platelets are
essential for the clotting of blood.

Blood smear
Platelet
White blood cell
(leukocyte)
Red blood cell
(erythrocyte)
Blood plasma

MUSCULAR TISSUE
consists of elongated cells called
muscle fibers or myocytes that
can use ATP to generate force.
muscular tissue produces body
movements, maintains posture,
and generates heat
It also provides protection.

Based on its location and
certain structural and
functional features, muscular
tissue is classified into three
types:
Skeletal muscle tissue
Cardiac muscle tissue
Smooth muscle tissue

SKELETAL MUSCLE TISSUE
Description:
Long, cylindrical, striated fibers with many
peripherally located nuclei; voluntary
control.
Location:
Usually attached to bones by tendons.
Function:
Motion, posture, heat production, and
protection.

Cardiac muscle Tissue
Description:
Branched striated fibers with one or
two centrally located nuclei; contains
intercalated discs; involuntary control.
Location:
Heart wall.
Function:
Pumps blood to all parts of the body.

SMOOTH MUSCLE CELL
 Description:
 Spindle-shaped (thickest in middle and tapering at
both ends), nonstriated fibers with one centrally
located nucleus; involuntary control.
 Location:
 Iris of the eyes, walls of hollow internal structures such
as blood vessels, airways to the lungs, stomach,
intestines, gallbladder, urinary bladder, and uterus.
 Function:
 Motion (constriction of blood vessels and airways,
propulsion of foods through gastrointestinal tract,
contraction of urinary bladder and gallbladder).

NERVOUS TISSUE
Consists of only two principal types of cells:
neurons and neuroglia (glial cells).
Neurons, or nerve cells, are sensitive to various
stimuli.
They convert stimuli into electrical signals called
action potentials
(nerve impulses) and conduct these action
potentials to other neurons, to muscle tissue, or
to glands.
Most neurons consist of three basic parts: a cell
body and two kinds of cell processes—
dendrites and axons.

Neuron of spinal cord
Axon
Dendrite
Nucleus

GLIAL CELLS
 non-Neuronal cells
 Maintains homeostasis, forms myelin and provides
support and protection for neurons in central and
peripheral nervous systems.
 The types of glial cells in CNS are
 Oligodendrocytes
 Astrocytes
 Ependymal cells
 Microglia
 The types of glial cells in CNS are
 Schwann cells
 Satellite cells

GLIAL CELLS
Ependymal cells
astrocytes
Microglial cells
oligodendrocytes

FAQs
Write notes on:
Enumerate the functions of epithelial
tissue
Characteristic features of muscular
tissues
Give the classification of connective
tissue. What are its functions?
Name the primary tissues. Give the
salient features of any one of them.
Connective tissues.

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