BODY TISSUES
O VERVIEW

Human body starts with one cell

Division makes millions of cells

Each specialized for particular functions

Some are so specialized, they can create hazards


Ex. Heart cells
Groups of similar cells that are similar in
structure and function: tissues
T YPES
OF
T ISSUES

Epithelium (covering)

Connective (support)

Nervous (control)

Muscle (movement)

All interweave to form the fabric of the body

Tissues organized into organs

One organ can be composed of several tissue
types
E PITHELIAL T ISSUE

Also called epithelium

Lining, covering, and glandular

Forms glands

Covers all free body surfaces

Versatile cells

Outer skin layer, and lining of body cavities

Every substance entering or leaving must pass
through these cells
S PECIAL C HARACTERISTICS

Except for glandular, they fit closely together to
form continuous sheets

Always have one free surface (apical surface):
exposed to body’s exterior or the cavity of an
internal organ

Lower surface rests on a basement membrane,
structureless material secreted by cells

No blood supply of their own (avascular);
depend on diffusion from capillaries

Regenerate themselves very easily
C LASSIFICATION OF
E PITHELIUM

Two names

First name is for number of cells: simple (one) or
stratified (more than one)

Second name describes shape: squamous
(flattened), cuboidal (cube-shaped), and
columnar (column-shaped)

Names are combined

*Stratified epithelia are named for the cells at the
free surface of the membrane, not the those
resting on the basement membrane
S IMPLE E PITHELIA

Most concerned with absorption, secretion, and
filtration

Simple Squamous epithelium

Single layer resting on basement membrane

Fit closely together

Usually forms membranes that use diffusion: air
sacs of lungs, walls of capillaries

Also forms serous membranes or serosae: slick
membranes lining ventral body cavity and cover
organs in ventral cavity
S IMPLE E PITHELIA

CONTD .
Simple Cuboidal Epi.

One layer resting on basement membrane

Common in glands and ducts: salivary glands and
pancreas

Forms walls of the kidney tubules, and covers
surface of the ovaries
S IMPLE E PITHELIA


CONTD .
Simple Columnar Epi.

One layer of tall cells

Fit close together

Goblet cells: produce a lubricating mucus, often
seen in this type of epithelium

Lines entire length of digestive tract from
stomach to anus
*Epithelial membranes that line body cavities
open to the exterior are called mucous
membranes or mucosae
S IMPLE E PITHELIA

CONTD .
Pseudostratified Columnar Epi.

Rest on basement membrane

Cells are different heights, and nuclei appear at
different heights above basement

Give false (pseudo) impression of stratified

Mainly absorption and secretion

Pseudostratified ciliated columnar epithelium

Ciliated, lines most of respiratory tract

Goblet cells produce mucus to trap dust and
debris
S TRATIFIED E PITHELIA

Two or more cell layers

More durable than simple

Primarily for protection

Stratified Squamous Epithelium

Most common stratified

Usually several layers

Free edge are squamous, closer to basement are
cuboidal or columnar

Found in “high friction” areas: esophagus, mouth,
other parts of skin
S TRATIFIED E PITHELIA

Stratified Cuboidal and Columnar Epithelia

Usually just two cell layers with (at least) the
surface cells being cuboidal

Surface cells of stratified columnar are columnar,
but its basal cells vary in size and shape

Both are fairly rare

Found mainly in the ducts or large glands
S TRATIFIED E PITHELIA

Transitional Epithelium

Highly modified

Stratified squamous epithelium

Forms lining of only a few organs: bladder, the
ureters, and part of the urethra

All part of the urinary system and undergo
considerable stretching

Basal layer are cuboidal or columnar; those at the
free surface vary in appearance

Stretching changes shape, cells can flatten and
become squamous-like
G LANDULAR E PITHELIA

Gland: consists of one more cells that make and
secrete a particular product

Secretion: typically contains protein molecules in an
aqueous fluid

Noun and verb: glandular cells obtain needed
materials from the blood and use them to make their
secretion, which they then discharge

Two types:

Endocrine glands: no connection to surface
(ductless), secrete hormones through diffusion

Exocrine glands: retain ducts, secretions empty to
surface: sweat and oil glands, liver and pancreas,
internal and external
C ONNECTIVE T ISSUE

Connects body parts

Found everywhere in body

Most abundant and widely distributed

Protect, support, bind other tissues together

Most are well vascularized (good blood supply)


Exceptions: tendons and ligaments have poor and
cartilage has none (tend to heal slower than the
others)
Extracellular matrix: nonliving substance found
outside of these cells
E XTRACELLULAR M ATRIX

Only found in connective tissue

Produced by the connective tissue cells then
secreted to their exterior

Two main elements:

Structureless ground substance: water +
adhesion proteins and large charged
polysaccharide molecules; like the “glue”
between these cells

Fibers: collagen (white) very strong; elastic
(yellow) stretching; reticular (fine collagen fibers)
make up internal “skeleton” of soft organs such
as spleen
E XTRACELLULAR M ATRIX

Because of matrix, connective tissue is able to
form a soft packing tissue around other organs,
to bear weight, and to withstand stretching and
other abuses

Varies depending on tissue type:

Fat tissue is mostly cells and the matrix is soft

Bone and cartilage have very few cells and large
amounts of hard matrix which makes them strong
T YPES OF C ONNECTIVE
T ISSUE

From most rigid to softest:

Bone

Cartilage

Dense Connective tissue

Loose Connective tissue

Blood
B ONE

Called Osseous tissue

Composed of bone cells sitting in cavities called
lacunae

Surrounded by layers of a very hard matrix that
contains calcium salts and collagen fibers

Exceptional ability to protect and support
B ONE P ICTURE
C ARTILAGE

Less hard and more flexible than bone

Found only in a few places

Most widespread is hyaline cartilage: lots of
collagen fibers, glassy, blue-white appearance

Forms larynx, attaches ribs to breastbone, covers
the ends of bones; skeleton of fetus

Fibrocartilage: highly compressible, forms disks
between the vertebrae of spinal column

Elastic Cartilage: found where elasticity is
desired; external ear
H YALINE C ARTILAGE P ICTURE
F IBROCARTILAGE P ICTURE
E LASTIC C ARTILAGE P ICTURE
D ENSE C ONNECTIVE T ISSUE

Also called dense fibrous tissue

Collagen fibers as its main matrix element

Between collagen fibers are rows of fibroblasts
(fiber-forming cells)

Forms strong, rope-like structures such as
tendons (attach skeletal muscles to bones) and
ligaments (connect bones to bones at joints)

Also makes up lower layers of skin (dermis),
arranged in sheets
D ENSE C ONNECTIVE T ISSUE
P ICTURE
L OOSE C ONNECTIVE T ISSUE

Softer and have more cells and fewer fibers

3 types:

Areolar: most widely distributed of connective;
soft, pliable, “cobwebby”; cushions and protects;
universal packing tissue; holds internal organs
together and in place; lamina propria underlies all
mucous membranes; all types of fibers forming
loose network; provides reservoir of water and
salts for surrounding tissues; inflammation in the
body causes this tissue to soak up excess fluid like a
sponge which causes it become puffy: edema;
phagocytes wander through looking for debris to
destroy
A REOLAR T ISSUE P ICTURE
A DIPOSE T ISSUE

Commonly called fat

Areolar with fat cells dominate

Fat cells = signet ring cells: cells are full of oil – pushes
nucleus to outer rim of cell

Forms subcutaneous tissue beneath skin

Insulates and protects from heat and cold

Protects some organs: kidneys, eyeballs in sockets

Fat depots in body: hips and breasts where fat is
stored and available for energy if needed
A DIPOSE T ISSUE P ICTURE
R ETICULAR T ISSUE

Delicate network of interwoven reticular fibers
associated with reticular cells

Forms the stroma: internal framework, which
can support many free blood cells (mostly
lymphocytes) in lymphoid organs such as lymph
nodes, the spleen, and bone marrow
R ETICULAR T ISSUE P ICTURE
B LOOD

Vascular tissue

Consists of blood cells, surrounded by nonliving,
fluid matrix called blood plasma

“fibers” in blood are soluble proteins that only
become visible during clotting

Transport vehicle for the cardiovascular system

Carries nutrients, wastes, respiratory gases, and
many other substances
B LOOD T ISSUE P ICTURE
M USCLE T ISSUE

Highly specialized to contract or shorten

Produce movement

Three types:

Skeletal muscle

Cardiac muscle

Smooth muscle
S KELETAL M USCLE

Packaged by connective tissue sheets into organs
called skeletal muscles, which are attached to the
skeleton

Controlled voluntarily (consciously)

Form the flesh of the body: the muscular system

When they contract they pull on bones or skin

Cells are long, cylindrical, multinucleate, and
striations (stripes)

Often called muscle fibers
S KELETAL M USCLE T ISSUE
S KELETAL M USCLE T ISSUE
C ARDIAC M USCLE

Found only in heart

Has striations

Uninucleate

Short

Branching cells that fit tightly together at junctions
called intercalated discs

Allow for rapid conduction of electrical impulses

Controlled involuntarily
C ARDIAC M USCLE T ISSUE
C ARDIAC M USCLE T ISSUE
S MOOTH M USCLE

Also called visceral muscle

No striations visible

Single nucleus, and spindle shaped (pointed at ends)

Walls of hollow organs: stomach, bladder, uterus, and
blood vessels

Contracts slower than other types

Peristalsis: wavelike motion that keeps food moving
through small intestine
S MOOTH M USCLE T ISSUE
S MOOTH M USCLE T ISSUE
N ERVOUS T ISSUE

Cells called neurons

Receive and conduct electrochemical impulses from one
body part to another

Irritability and conductivity are major functions

Unique structure

Cytoplasm drawn out into long processes (extensions) as
much as 3 ft or more in the leg

Supporting cells: insulate, support, and protect the
delicate neurons

Make up nervous system: brain, spinal cord, and nerves
N ERVOUS T ISSUE