Tissue

Human anatomy
Unit III

Definition of Tissues

Biological tissue is a collection of interconnected

cells that perform a similar function within an

organism.

In other words, it is a group of cells working

together mainly inside an organ.

Classification of Tissues
Human body is composed of

4 basic types of tissue:

•Epithelial tissue

•Connective tissue

•Muscular tissue

•Nervous tissue

Origin of Tissue
A fertilized egg divides to produce 3 primary germ cell

layers. These layers differentiate to form the tissues of the

body.

Epithelial Tissue

Epithelial cells cover or line all body surfaces, cavities and

tubes. So, These are called covering epithelia.

Epithelial cells form the functional units of secretory glands.

So, These are called glandular epithelia.

General Characteristic

 Closely attached to each other forming a protective barrier.

 Always has one free (apical) surface open to outside the body or

inside (cavity) an internal organ.

 Always has one fixed (basal) section attached to underlying

connective tissue.

 Has no blood vessels but can soak up nutrients from blood vessels

in connective tissue underneath.

 Can have lots of nerves in it (innervated).

 Very good at regenerating (fixing itself). i.e. sunburn, skinned

knee.

Functions
 To protect the tissues that lie beneath it

from radiation, desiccation, toxins, invasion by pathogens, and

physical trauma.

 The regulation and exchange of chemicals between the underlying

tissues and a body cavity.

 The secretion of hormones into the blood vascular system, and/or

the secretion of sweat, mucus, enzymes, and other products that are

delivered by ducts glandular epithelium.

 To provide sensation.

 Absorbs stomach and intestinal lining (gut).

 Filters the kidney.

 Forms secretary glands.

Classification of Epithelia
According to thickness

 “simple” – one cell layer

 “stratified” – more than one layer of cells (which are

named according to the shape of the cells in the

apical layer)

According to shape

 “squamous” – wider than tall

 “cuboidal” – as tall as wide

 “columnar” – taller than wide

Simple squamous epithelium

Description: Single layer of
flattened cells with disc-shaped
central nuclei and sparse
cytoplasm; the simplest of the
epithelia.

Function: Passive transport of gases
and fluids.

Location:Alveoli of lungs, lining
body cavities (mesothelium), lining
blood vessels (endothelium)

Simple cuboidal epithelia
Description : Single layer of
cubelike cells with large,
spherical central nuclei.

Function : Secretion and
absorption.

Location: Kidney tubules;
ducts and secretory portions
of small glands; ovary
surface.

Simple columnar epithelia
Description: Single layer of tall
cells with round to oval
nuclei.

Types: (i)Ciliated columnar
epithelia.

(ii)Non-ciliated
columnar epithelia.

Function: Absorption;
secretion of mucus,
Enzymes and other
substances.

Location: Digestive tract, gall
bladder etc.

Stratified squamous epithelia
Description:
Multilayered, surface cell are
squamous, basal cells are
cuboidal and divided
constantly.

Function: Protection.

Location: Oral
cavity, cervix, anal canal.

Stratified cuboidal epithelia
Description: Generally two
layers of cube-like cells.

Function: Protection.

Location: Large ducts of sweat
glands, mammary glands,
and salivary glands.

Stratified columnar epithelia
Description:
Multilayered, superficial cells
elongated and columnar.

Function: Protection;
secretion.

Location: Rare in the body;
small amount in the male
urethra.

Pseudo stratified columnar
epithelia

Description: Single cell layered,
all cell attach to the basement
membrane but not all reach the
free surface. Nuclei at varying
depth.

Function: Secretion of mucus,
propulsion of mucus by ciliary
action.

Location: Lines of trachea.

Transitional epithelia
Description: Characterized by
domelike cells that are neither
squamous nor columnar. The
form of the cells changes.

Function: Stretching and
protection.

Location: Bladder and part of
urethra.

Connective Tissues

The tissues that connect the different parts of the

body together are called connective tissues.

General characteristic
 The intercellular material is maximum where as the

cellular component is minimum.

 Unlike the other tissues, (e.g. epithelium, muscle and

nerve) which are formed mainly by cells, the major

constituent of connective tissue is ECM (Extra-cellular

matrix).

 Possess cells, fibers and ground substances.

Basic Functions

 Support and binding of other tissues

 Holding body fluids

 Defending the body against infection

 macrophages, plasma cells, mast cells, WBCs

 Storing nutrients as fat

Classification of connective
tissues

Connective tissue proper :
Loose CT ; Areolar

Description: Gel like matrix with
all three fiber types ; cells:
fibroblasts, macrophages, mast
cells, and white blood cells.

Function: Its macrophages
phagocytize bacteria ; plays
important role in inflammation ;
holds and conveys tissue fluid.

Location: Distributed under
epithelia of body; surrounds
capillaries.

CT proper : Loose CT ; Adipose
Description: Matrix as in areolar,
but very sparse; closely packed
adipocytes, or fat cells , have Fat droplets
nucleus pushed to the side by
large fat droplet.

Nucleus

Function: Provides reverse food
fuel; insulates against heat loss;
supports and protects organs.

Location: Under skin; around
kidneys and eyeballs; within
abdomen; in breasts.

CT proper: Loose CT; reticular

Description: Network of reticular
fibers in a typical loose ground
substance; reticular cells lie on
the network.

Function: Fibers form a soft internal
skeleton that supports other cell
types including white blood cells,
mast cells, and macrophages.

Location: Lymphoid organs(lymph
nodes, bone marrow, and
macrophages.

CT proper: dense CT; Irregular
Description: Primarily irregularly
arranged collagen fibers; some
elastic fibers; major cell type is
the fibroblast.

Function: Elasticity and structural
support. Collagen

fibers

Location: Dermis of the skin;
submucosa of digestive tract and
joints.

CT proper: dense CT; Regular

Description: Primarily parallel
collagen fibers; a few elastin
fibers; major cell type is the
fibroblast.

Function: Attaches muscles to
bones and bones to bones.

Location: Tendons and in most
ligaments.

Cartilage: Hyaline
Description: Amorphous but firm
matrix; chondroblasts produce
the matrix and when mature lie
in lacunae.

Function: Supports and
reinforces; resists compressive
stress.

Location: Forms most of the
embryonic skeleton; ends of
long bones; cartilages of nose.

Cartilage: Elastic
Description: Similar to hyaline
cartilage, but more elastic
fibers in matrix.

Function: Maintains the shape
and allows flexibility.

Location: Supports the external
ear(pinna).

Cartilage : Fibrocartilage

Description : Collagen fibers
are predominant ; matrix is
as hyaline but less firm.

Function: High tensile
strength, absorb
compressive shock.

Location: Intervertebral disc;
discs of knee joint.

Bone
Description: Hard, calcified
matrix containing many
collagen fibers. Very well
vascularized.

Function: Bone supports and

protects; provides levers for
the muscles to act on; stores
calcium and other minerals
and fat; bone marrow is the
site of blood cell formation.

Location: Skeleton.

Blood
Description: Liquid connective
tissue, red and white blood
cells in fluid matrix.

Function: Transport respiratory
gases, nutrients, wastes and
other substances.

Location: In the blood vessels.

Muscle Tissue

 Muscle is one of our 4 tissue types and muscle tissue
combined with nerves, blood vessels, and various
connective tissues.

 Muscles are quite complex and as we’ll find out, they

are a marvel of both biology and physics.

General characteristics
1. Excitability

 The ability to receive and respond to a stimulus
 In skeletal muscle, the stimulus is a neurotransmitter

(chemical signal) release by a neuron (nerve cell).
 In smooth muscle, the stimulus could be a

neurotransmitter, a hormone, stretch, pH, Pco2, or
Po2.

 In cardiac muscle, the stimulus could be a
neurotransmitter, a hormone, or stretch.

 The response is the generation of an electrical impulse

that travels along the plasma membrane of the muscle
cell.

2. Contractility

 The ability to shorten forcibly when adequately
stimulated.

 This is the defining property of muscle tissue.

2. Extensibility

 The ability to be stretched (Extended)

4. Elasticity

 The ability to recoil and resume original length
after being stretched.

Functions
 Movement

 Locomotion

 Maintains posture

 Produces heat

 Facial expressions

 Pumps blood

 Peristalsis

3 Types of Muscle Tissue

Skeletal Muscle Tissue
Description: Long striated cells
with multiple nuclei.

Function: Contraction for
voluntary movements.

Location: In skeletal muscle.

Smooth Muscle Tissue
Description: Long, spindle-

shaped cells, each with a

single nucleus.

Function: Propulsion of

substances along internal

passageways.

Location: In hollow organs(e.g.

stomach)

Cardiac Muscle tissue
Description:
Branching, striated cells
fused at plasma
membranes.

Function: Pumping of
blood in the circulatory
system.

Location: Wall of heart.

Nerve Tissue
By far the most complex tissue in the human body is

nerve tissue.

Formed by a network of more than 100 million nerve
cells, assisted by many more glial cells.

Each neuron has, on an average , at least a
thousand interconnection with other neurons forming
a very complex nervous system.

Functions

 Regulates & controls body functions

 Generates & transmits nerve impulses

 Supports, insulates and protects impulse

generating neurons.

Composition of Nerve Tissue
The nerve tissue is composed of two elements:

1. The nerve cell or neuron

2. The neuroglia

Neuron

Description: Neurons are
branching cells; cell processes
that may be quite long extend
from the nucleus-containing cell
body.

Function: Transmit electrical
signals from sensory receptors
and to effectors(muscles and
glands) that control their
activity.

Location: Brain, spinal cord and
nerves.

Glial cells
Glia carry nutrients, speed

repair, provide myelin for

axons, support the blood-

brain barrier, and may form

their own communication

network. They are also

involved in neurogenesis.