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Chapter 5: Tissues
Anatomy & Physiology
Ch. 5 Wordbytes
1.
2.
3.
4.
5.
6.
7.
8.
9.
adip- = fat
areola- = open
space
chondr- = cartilage
-crine = secretion
-ectomy = to cut out
epi- = upon
exo- = outer
-glia = glue
hist- = tissue
10. meso- = middle
11. neuro- = nerve
12. os- = bone
13. pseudo- = false
14. retic- = net
15. squam- = scale
16. strat- = layer
17. viscero- = body
organ
Chapter 5 Tissues

Cells are highly organized living units, but they
typically do not function alone. Instead, cells work
together in groups called tissues groups of similar
cells that function together to carry out specialized
activities.
Histology is the science that deals with the study of
tissues.
A pathologist is a physician who specializes in
laboratory studies of cells and tissues to help other
physicians make accurate diagnoses; they examine
tissues for any changes that might indicate disease.
I. Types of Tissue:
Body tissues are classified into four basic types
based on their structure and functions:
1. Epithelial tissue covers body surfaces; lines body cavities, hollow
organs, and ducts (tubes); and forms glands.
2. Connective tissue protects and supports the body and its organs,
binds organs together, stores energy reserves as fat, and
provides immunity.
3. Muscular tissue generates the physical force needed to make
body structures move.
4. Nervous tissue detects changes inside and outside the body and
initiates and transmits nerve impulses (action potentials) that
coordinate body activities to help maintain homeostasis.
Cell Junctions: Most cells are tightly joined into
functional units by points of contact between their
plasma membranes called cell junctions.
1. Some fuse cells together so tightly that they prevent
substances from passing between the cells.
Important for tissues that line the stomach, intestines, and
urinary bladder prevents the contents from leaking out.
2. Others hold cells together so that they don’t separate while
performing their functions.
3. Still others form channels that allow ions and molecules to
pass between cells = permits cells in a tissue to
communicate with each other, enables nerve or muscle
impulses to spread rapidly among cells.
II. Epithelial Tissue:
A. Two types of epithelial tissue (epithelium):
(1) Covering and lining epithelium forms outer
covering of the skin and some internal organs; lines
body cavities, blood vessels, ducts, and the interiors
of the respiratory, digestive, urinary, and
reproductive systems.
It makes up, along with nervous tissue, the parts of
the sense organs for hearing, vision, and touch
(2) Glandular epithelium makes up the secreting
portion of glands, such as sweat glands.
B. General Features of Epithelial Tissue
1. Epithelium consists of closely packed cells with little extracellular
material between them, and the cells are arranged in continuous
sheets, in either single or multiple layers.
2. Epithelial cells have a(n):
a. apical (free) surface, which is exposed to a body cavity,
lining of an internal organ, or the exterior of the body
b. lateral surfaces, which face adjacent cells on either side
c. basal surface, which is attached to a basement membrane.
B. General Features of Epithelial Tissue
3. Epithelia are avascular = they lack blood vessels. The
vessels that supply nutrients to and remove wastes
from epithelia are located in adjacent connective
tissues. They exchange materials by diffusion.
4. Epithelia have a nerve supply.
5. Because epithelium is subject to a certain amount of
wear and tear and injury, it has a high capacity for
renewal by cell division.
C. Covering and Lining Epithelium:
1. Arrangement of cells in layers. Cells are arranged
depending on the functions the epithelium
performs:
a. Simple epithelium single layer of cells that functions in
diffusion, osmosis, filtration, secretion (production/release of
mucus/sweat/enzymes), and absorption (intake of
fluids/substances).
b. Pseudostratified epithelium appears to have multiple layers of
cells because the cell nuclei lie at different levels and not all cells
reach the apical surface.
c. Stratified epithelium consists of two or more layers of cells that
protect underlying tissues where there is considerable wear and
tear.
2. Cell shapes:
a. Squamous cells flat, arranged like floor tiles, and thin =
rapid passage of substances.
b. Cuboidal cells as tall as they are wide, and shaped like
cubes or hexagons; may have microvilli and function in either
secretion or absorption.
c. Columnar cells much taller than they are wide (like
columns) and protect underlying tissues. May have cilia or
microvilli, and often are specialized for secretion and absorption.
d. Transitional cells change shape, from flat to cuboidal, as
organs (like urinary bladder) stretch to a larger size and then
collapse to a smaller size.
Simple Epithelium:
A. Simple squamous epithelium
–
Description: Single layer of flat cells; centrally
located nucleus.
–
Location: Lines heart, blood vessels, lymphatic
vessels, air sacs of lungs, Bowman’s capsule of
kidneys, and inner surface of the eardrum; forms
epithelial layer of serous membranes, such as the
peritoneum.
–
Function: Filtration, diffusion, osmosis, and secretion
in serous membranes.
B. 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.
–
Function: Secretion and absorption.
C. Nonciliated simple columnar
epithelium
–
Description: Single layer of nonciliated columnlike cells with nuclei near bases of cells; contains
goblet cells and cells with microvilli in some
locations.
–
Location: Lines most of the gastrointestinal tract
(from the stomach to the anus), ducts of many
glands, and gallbladder.
–
Function: Secretion and absorption.
D. Ciliated simple columnar
epithelium
–
Description: Single layer of ciliated column-like
cells with nuclei near bases; contains goblet cells in
some locations.
–
Location: Lines a few portions of upper respiratory
tract, uterine (fallopian) tubes, uterus, some
paranasal sinuses, and central canal of spinal cord.
–
Function: Moves mucus and other substances by
ciliary action.
E. 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.
Stratified Epithelium
F. 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 epiglottis, part of
pharynx, and vagina, and covers the tongue.
–
Function: Protection.
G. Stratified cuboidal epithelium
–
Description: Two or more layers of cells in which
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.
H. 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 a
part of the conjunctiva of the eye.
–
Function: Protection and secretion.
I. 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 distention.
Glandular Epithelium
J. 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, 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.
K. 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.
III. Connective Tissue
Connective tissue is one of the most abundant and
widely distributed tissues in the body. In its various
forms, connective tissue 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;
is the major transport system within the body
(blood, a fluid connective tissue);
is the major site of stored energy reserves
(adipose, or fat tissue); and
is the main site of immune responses.
A. General Features of Connective
Tissue
1.
Two basic elements: cells and extracellular matrix the
material between its widely spaced cells. The extracellular
matrix consists of protein fibers and ground substance, the
material between the cells and the fibers. The extracellular
matrix is usually secreted by the connective tissue cells and
determines the tissue’s qualities (in cartilage, matrix is firm but
pliable; in bone, it is hard and not pliable.
2.
Unlike epithelia: Connective tissues do not usually occur on
body surfaces, and usually are highly vascular (have a rich
blood supply). Exceptions include cartilage, which is
avascular, and tendons, with a scanty blood supply. Like
epithelia: Except for cartilage, connective tissues are supplied
with nerves.
B. Connective Tissue Cells
1. Fibroblasts large, flat cells with branching processes present in several
connective tissues, and usually the most numerous. Fibroblasts migrate through
the connective tissue, secreting the fibers and ground substance of the
extracellular matrix.
2. Macrophages develop from monocytes, a type of white blood cell. Macrophages
have an irregular shape with short branching projections and are capable of
engulfing bacteria and cellular debris by phagocytosis.
3. Plasma cells small cells that develop from a type of white blood cell called a B
lymphocyte. Plasma cells secrete antibodies, proteins that attack or neutralize
foreign substances in the body = important part of the body’s immune response.
4. Mast cells abundant alongside the blood vessels that supply connective tissue.
They produce histamine, a chemical that dilates small blood vessels as part of the
inflammatory response, the body’s reaction to injury or infection. Mast cells can
also kill bacteria.
5. Adipocytes fat cells or adipose cells, are connective tissue cells that store
triglycerides (fats). They are found below the skin and around organs such as the
heart and kidneys.
Representative cells and fibers present
in connective tissues
C. Connective Tissue
Extracellular Matrix
Each type of connective tissue has unique
properties, based on the specific extracellular
materials between the cells.
The extracellular matrix consists of a fluid,
gel, or solid ground substance plus protein
fibers.
1. Ground Substance

Ground substance, the component of a connective
tissue between the cells and fibers, supports cells,
binds them together, and provides a medium through
which substances are exchanged between the blood
and cells. The ground substance plays an active role
in how tissues develop, migrate, proliferate, and
change shape, and in how they carry out their
metabolic functions.

Ground substance contains water and an assortment
of large organic molecules, many of which are
complex combinations of polysaccharides and
proteins.
2. Fibers

Fibers in the extracellular matrix strengthen
and support connective tissues.
Three types of fibers are embedded in the
extracellular matrix between the cells:
collagen fibers,
elastic fibers, and
reticular fibers.
a. Collagen Fibers
1.
Very strong and resist pulling forces, but they are
not stiff, which promotes tissue flexibility.
2.
Often occur in bundles lying parallel to one another
= great strength.
3.
Consist of the protein collagen = the most abundant
protein in your body, representing about 25% of total
protein. Found in most types of connective tissues,
especially bone, cartilage, tendons, and ligaments.
ligaments

Despite their strength, ligaments may be
stressed beyond their normal capacity. This
results in sprain, a stretched or torn ligament.
The ankle joint is most frequently sprained.
Because of their poor blood supply, the
healing of even partially torn ligaments is a
very slow process; completely torn ligaments
require surgical repair.
b. Elastic Fibers
1.
Smaller in diameter than collagen fibers; branch and join together to
form a network within a tissue.
2.
Consists of elastin (protein) surrounded by fibrillin (glycoprotein),
which is essential to the stability of an elastic fiber.
3.
Strong, but can be stretched up to one-and-a-half times their
relaxed length without breaking; also have the ability to return to
their original shape after being stretched = elasticity.
4.
Plentiful in skin, blood vessel walls, and lung tissue.
Marfan syndrome (MAR-fan) is an inherited
disorder caused by a defective fibrillin gene.

The result is abnormal development of elastic fibers. Tissues rich in
elastic fibers are malformed or weakened.

Structures affected most seriously are the covering layer of bones
(periosteum), the ligament that suspends the lens of the eye, and the
walls of the large arteries.

People with Marfan syndrome tend to be tall and have
disproportionately long arms, legs, fingers, and toes. A common
symptom is blurred vision caused by displacement of the lens of the
eye.

The most life-threatening complication of Marfan syndrome is
weakening of the aorta (the main artery that emerges from the heart),
which can suddenly burst.
c. Reticular fibers
1.
Consist of collagen and a coating of glycoprotein,
provide support in the walls of blood vessels and
form branching networks around fat cells, nerve
fibers, and skeletal and smooth muscle cells.
2.
Much thinner than collagen fibers, but like collagen
fibers, provide support and strength and also form
the stroma (= bed or covering) or supporting
framework of many soft organs, such as the spleen
and lymph nodes. These fibers also help form the
basement membrane.
Loose Connective Tissue
A. Areolar connective tissue
–
Description: Consists of fibers (collagen, elastic, and
reticular) and several kinds of cells (fibroblasts,
macrophages, plasma cells, adipocytes, and mast cells)
embedded in a semifluid ground substance.
–
Location: Subcutaneous layer deep to skin; superficial
region of dermis of skin; lamina propria of mucous
membranes; and around blood vessels, nerves, and body
organs.
–
Function: Strength, elasticity, and support.
B. Adipose tissue
–
Description: Consists of adipocytes, cells specialized to store
triglycerides (fats) as a large centrally located droplet; nucleus
and cytoplasm are peripherally located.
–
Location: Subcutaneous layer deep to skin, around heart and
kidneys, yellow bone marrow, and padding around joints and
behind eyeball in eye socket.
–
Function: Reduces heat loss through skin, serves as an
energy reserve, supports, and protects.
Dense Connective Tissue
C. Dense regular connective tissue
–
Description: Extracellular matrix looks shiny white; consists
mainly of collagen fibers regularly arranged in bundles;
fibroblasts present in rows between bundles.
–
Location: Forms tendons (attach muscle to bone), most
ligaments (attach bone to bone), and aponeuroses
(sheetlike tendons that attach muscle to muscle or muscle
to bone).
–
Function: Provides strong attachment between various
structures.
D. Dense irregular connective
tissue
–
Description: Consists predominantly of collagen fibers
randomly arranged and a few fibroblasts.
–
Location: Fasciae (tissue beneath skin and around
muscles and other organs), deeper region of dermis of skin,
periosteum of bone, perichondrium of cartilage, joint
capsules, membrane capsules around various organs
(kidneys, liver, testes, lymph nodes), pericardium of the
heart, and heart valves.
–
Function: Provides strength.
E. Elastic connective tissue
–
Description: Consists predominantly of freely
branching elastic fibers; fibroblasts are present in
spaces between fibers.
–
Location: Lung tissue, walls of elastic arteries,
trachea, bronchial tubes, true vocal cords,
suspensory ligament of penis, and ligaments
between vertebrae.
–
Function: Allows stretching of various organs.
F. Reticular connective tissue
–
Description: A network of interlacing reticular fibers and
reticular cells.
–
Location: Stroma (supporting framework) of liver, spleen,
lymph nodes; red bone marrow, which gives rise to blood
cells; reticular lamina of the basement membrane; and
around blood vessels and muscles.
–
Function: Forms stroma of organs; binds together smooth
muscle tissue cells; filters and removes worn-out blood cells
in the spleen and microbes in lymph nodes.
Cartilage
G. Hyaline cartilage
–
Description: Consists of a bluish-white, shiny ground
substance with 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.
H. Fibrocartilage
–
Description: Consists of chondrocytes scattered
among 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.
Loose Connective Tissue
I. 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.
Bone Tissue

Bones are organs composed of several different
connective tissues, including bone or osseous tissue.
Bone tissue has several functions.

It supports soft tissues, protects delicate structures,
and works with skeletal muscles to generate
movement.

Bone stores calcium and phosphorus; stores red bone
marrow, which produces blood cells; and houses
yellow bone marrow, a storage site for triglycerides.
Liquid Connective Tissue
1.
Blood tissue (blood) connective tissue with a liquid extracellular
matrix called blood plasma = pale yellow fluid that consists
mostly of water with a wide variety of dissolved substances:
nutrients, wastes, enzymes, hormones, respiratory gases, and
ions. Suspended in the plasma are red blood cells, white blood
cells, and platelets. Red blood cells transport O2 to body cells and
remove CO2 from them. White blood cells are involved in
phagocytosis, immunity, and allergic reactions. Platelets
participate in blood clotting.
2.
Lymph fluid that flows in lymphatic vessels. It is a connective
tissue that consists of several types of cells in a clear
extracellular matrix similar to blood plasma but with much less
protein.
IV. Muscular Tissue

Muscular tissue consists of elongated cells called muscle fibers that
are highly specialized to generate force. As a result of this
characteristic, muscular tissue produces motion, maintains posture,
and generates heat. It also offers protection. Based on its location
and certain structural and functional characteristics, muscular tissue
is classified into three types:
1.
Skeletal muscle tissue is named for its location—it is usually attached to
the bones of the skeleton.
2.
Cardiac muscle tissue forms the bulk of the wall of the heart.
3.
Smooth muscle tissue is located in the walls of hollow internal structures
such as blood vessels, airways to the lungs, the stomach, intestines,
gallbladder, and urinary bladder.
V. Nervous Tissue

Despite the awesome complexity of the
nervous system, it consists of only two
principal types of cells:
1.
2.
Neurons or nerve cells sensitive to various
stimuli; convert stimuli into nerve impulses
(action potentials) and conduct these impulses to
other neurons, to muscle fibers, or to glands.
Neuroglia do not generate or conduct nerve
impulses, but they do have many other important
supportive functions.
VI. Membranes

Membranes flat sheets of pliable tissue that cover
or line a part of the body. The combination of an
epithelial layer and an underlying connective tissue
layer constitutes an epithelial membrane.

The principal epithelial membranes of the body are
mucous membranes, serous membranes, and the
cutaneous membrane, or skin. Another kind of
membrane, a synovial membrane, lines joints and
contains connective tissue but no epithelium.
A. Mucous Membranes
1.
Lines a body cavity that opens directly to the exterior = line the
entire digestive, respiratory, and reproductive systems and
much of the urinary system.
2.
The epithelial layer of a mucous membrane secretes mucus,
which prevents the cavities from drying out. It also traps
particles in the respiratory passageways, lubricates and
absorbs food as it moves through the gastrointestinal tract,
and secretes digestive enzymes.
3.
The connective tissue layer helps bind the epithelium to the
underlying structures. It also provides the epithelium with
oxygen and nutrients and removes wastes via its blood
vessels.
B. Serous Membranes:
Line body cavities that don’t open directly to the exterior,
and it also covers the organs that lie within the cavity.
1.
Two parts:
a. Parietal layer part attached to the cavity wall
b. Visceral layer part that covers and attaches to the organs inside these
cavities. Each layer consists of areolar connective tissue covered by
mesothelium. Mesothelium is a simple squamous epithelium.
It secretes serous fluid, a watery lubricating fluid that allows organs to
glide easily over one another or to slide against the walls of cavities.
2.
The serous membrane lining the thoracic cavity and covering the
lungs is the pleura.
The serous membrane lining the heart cavity and covering the heart
is the pericardium.
The serous membrane lining the abdominal cavity and covering the
abdominal organs is the peritoneum.
Synovial Membranes
1.
Line the cavities of some joints.
2.
Composed of areolar connective tissue and adipose
tissue with collagen fibers; no epithelial layer.
3.
Contain cells which secrete synovial fluid to
lubricate the ends of bones as they move at joints,
nourish the cartilage covering the bones, and
remove microbes and debris from the joint cavity.
VII. Tissue Repair




New cells from stroma or parenchyma
Epithelial cells originate from stem cells in defined areas
of tissue layer
Bone regenerates readily, cartilage poorly
Muscular tissue can replace cells but slowly

Nerve tissue is poorest at replacement although some
stem cells seem to be available.

Replacement from stroma –> scar tissue & functional
loss.