CHAPTER 3: Cells and Tissues
Tissues - Groups of cells with similar structure and function
TYPES
● Epithelial Tissue
Locations: Hallmarks of epithelial tissues:
● Body coverings ● Cover and line body surfaces
● Body linings ● Often form sheets with one free
● Glandular tissue surface, the apical surface, and an
anchored surface, the basement
membrane
● Avascular (no blood supply)
● Regenerate easily if well nourished
Functions: Classification of epithelia
● Protection ● Number of cell layers
● Absorption ● Simple—one layer
● Filtration ● Stratified—more than one layer
● Secretion ● Shape of cells
● Squamous—flattened, like fish scales
● Cuboidal—cube-shaped, like dice
● Columnar—shaped like columns
● KINDS OF EPITHELIAL TISSUE
Simple Epithelia Simple Cuboidal Epithelium
● Functions in absorption, secretion, and ● Single layer of cubelike cells
filtration ● Locations
● Very thin (so not suited for ○ Common in glands and their
protection) ducts
○ Forms walls of kidney
tubules
○ Covers the surface of
ovaries
● Functions in secretion and
absorption; ciliated types propel
mucus or reproductive cells
Simple Squamous Epithelium Simple Columnar Epithelium
● Single layer of flat cells ● Single layer of tall cells
● Locations—usually forms membranes ● Goblet cells secrete mucus
○ Lines air sacs of the lungs ● Locations
○ Forms walls of capillaries ○ Lining of the digestive tract
○ Forms serous membranes from stomach to anus
(serosae) that line and cover ○ Mucous membranes
organs in ventral cavity (mucosae) line body cavities
● Functions in diffusion, filtration, or opening to the exterior
secretion in membranes ● Functions in secretion and
absorption; ciliated types propel
mucus or reproductive cell
Pseudostratified Columnar Epithelium Stratified Squamous Epithelium
● All cells rest on a basement membrane ● Most common stratified epithelium
● Single layer, but some cells are ● Named for cells present at the free
shorter than others giving a false (apical) surface, which are squamous
(pseudo) impression of stratification ● Functions as a protective covering
● Location: respiratory tract, where it is where friction is common
ciliated and known as pseudostratified ● Locations—lining of the:
ciliated columnar epithelium ○ Skin (outer portion)
● Functions in absorption or secretion ○ Mouth
○ Esophagus
Stratified Epithelia Stratified Columnar Epithelium
● Consist of two or more cell layers ● Surface cells are columnar, and cells
● Function primarily in protection underneath vary in size and shape;
functions in protection
Stratified Cuboidal Epithelium Stratified Cuboidal and Columnar
● Two layers of cuboidal cells; functions ● Rare in human body
in protection ● Found mainly in ducts of large glands
Transitional Epithelium Glandular Epithelia
● Composed of modified stratified ● One or more cells responsible for
squamous epithelium secreting a particular product
● Shape of cells depends upon the ● Secretions contain protein molecules
amount of stretching in an aqueous (water-based) fluid
● Functions in stretching and the ability ● Secretion is an active process
to return to normal shape
● Location: lining of urinary system
organs
● Two major gland types develop from epithelial sheets
○ Endocrine glands - Ductless; secretions (hormones) diffuse into blood
vessels. Examples include thyroid, adrenals, and pituitary
○ Exocrine glands - Secretions empty through ducts to the epithelial surface.
Include sweat and oil glands, liver, and pancreas (both internal and external)
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● Connective Tissue
Characteristics of connective tissue Two main elements of the extracellular matrix
● Variations in blood supply 1. Ground substance—mostly water, along
○ Some tissue types are well with adhesion proteins and
vascularized polysaccharide molecules
○ Some have a poor blood supply 2. Fibers
or are avascular a. Collagen (white) fibers
● Extracellular matrix b. Elastic (yellow) fibers
○ Nonliving material that c. Reticular fibers (a type of
surrounds living cells collagen)
Types of connective tissue from most rigid to softest, or most fluid:
Bone (osseous tissue) Dense connective tissue (dense fibrous
Composed of: tissue)
● Osteocytes (bone cells) sitting in ● Main matrix element is collagen fiber
lacunae (cavities) ● Fibroblasts are cells that make fibers
● Hard matrix of calcium salts ● Locations
● Large numbers of collagen fibers ○ Tendons—attach skeletal
● Functions to protect and support the muscle to bone
body ○ Ligaments—attach bone to
bone at joints and are more
elastic than tendons
○ Dermis—lower layers of the
skin
Cartilage Loose connective tissue
● Less hard and more flexible than bone ● Softer, have more cells and fewer
● Found in only a few places in the body fibers than other connective tissues
● Chondrocyte (cartilage cell) is the (except blood)
major cell type TYPES
TYPES ● Areolar connective tissue
● Hyaline cartilage ○ Most widely distributed
○ Most widespread type of connective tissue
cartilage ○ Soft, pliable tissue like
○ Abundant collagen fibers “cobwebs”
hidden by a glassy, rubbery ○ Functions as a universal
matrix packing tissue and “glue” to
○ Locations: Trachea ▪ Attaches hold organs in place
ribs to the breastbone ▪ ○ Layer of areolar tissue called
Covers ends of long bones ▪ lamina propria underlies all
Entire fetal skeleton prior to membranes
birth ▪ Epiphyseal (growth) ○ All fiber types form a loose
plates in long bones network
● Fibrocartilage ○ Can soak up excess fluid
○ Highly compressible (causes edema).
○ Location: forms cushions like ● Adipose connective tissue
discs between vertebrae of ○ An areolar tissue in which
the spinal column adipose (fat) cells dominate
● Elastic cartilage ○ Functions - Insulates the body
○ Provides elasticity ▪ Protects some organs ▪
○ Location: supports the Serves as a site of fuel
external ear storage
○ Locations - Subcutaneous
tissue beneath the skin ▪
Protects organs, such as the
kidneys ▪ Fat “depots” include
hips, breasts, and belly
● Reticular connective tissue
○ Delicate network of
interwoven fibers with
reticular cells (like
fibroblasts)
○ Forms stroma (internal
framework) of organs
○ Locations - Lymph nodes ▪
Spleen ▪ Bone marrow
Blood (vascular tissue)
● Blood cells surrounded by fluid matrix
known as blood plasma
● Soluble fibers are visible only during
clotting
● Functions as the transport vehicle for
the cardiovascular system, carrying:
○ Nutrients, Wastes,
Respiratory gases
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● Muscle Tissue
○ Function is to contract, or shorten, to produce movement
TYPES
Skeletal muscle tissue Cardiac muscle tissue
● Packaged by connective tissue ● Involuntarily controlled
sheets into skeletal muscles, which ● Found only in the heart
are attached to the skeleton and ● Pumps blood through blood
pull on bones or skin vessels
● Voluntarily (consciously) controlled ● Characteristics of cardiac
● Produces gross body movements or muscle cells
facial expressions ○ Striations
● Characteristics of skeletal muscle ○ One nucleus per
cells cell
● Striations (stripes) ○ Short, branching
● Multinucleate (more than one cells
nucleus) ○ Intercalated discs
● Long, cylindrical shape contain gap
junctions to
connect cells
together
Smooth (visceral) muscle tissue
● Involuntarily controlled
● Found in walls of hollow organs such
as stomach, uterus, and blood
vessels
● Peristalsis, a wavelike activity, is a
typical activity
● Characteristics of smooth muscle
cells
○ No visible striations
○ One nucleus per cell
○ Spindle-shaped cells
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● Nervous Tissue
○ Function is to receive and conduct electrochemical impulses to and from
body parts
■ Irritability
■ Conductivity
○ Composed of neurons and nerve support cells
○ Support cells called neuroglia insulate, protect, and support neurons
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● Tissue Repair (Wound Healing)
○ Occurs in two ways:
1. Regeneration - Replacement of destroyed tissue by the same kind of
cells
2. Fibrosis - Repair by dense (fibrous) connective tissue (scar tissue)
○ Whether regeneration or fibrosis occurs depends on:
1. Type of tissue damaged
2. Severity of the injury
○ Clean cuts (incisions) heal more successfully than ragged tears of the tissue
○ Events of tissue repair
■ Inflammation sets the stage
● Capillaries become very permeable
● Clotting proteins migrate into the area from the bloodstream
● A clot walls off the injured area
■ Granulation tissue forms
● Growth of new capillaries
● Phagocytes dispose of blood clot and fibroblasts
● Rebuild collagen fibers
■ Regeneration and fibrosis effect permanent repair
● Scab detaches
● Whether scar is visible or invisible depends on severity of
wound
○ Tissues that regenerate easily
○ Epithelial tissue (skin and mucous membranes)
■ Fibrous connective tissues and bone
○ Tissues that regenerate poorly
■ Skeletal muscle
○ Tissues that are replaced largely with scar tissue
■ Cardiac muscle
■ Nervous tissue within the brain and spinal cord
● Developmental Aspects of Cells and Tissues
○ Growth through cell division continues through puberty
○ Cell populations exposed to friction (such as epithelium) replace lost cells
throughout life
○ Connective tissue remains mitotic and forms repair (scar) tissue
○ With some exceptions, muscle tissue becomes amitotic by the end of
puberty
○ Nervous tissue becomes amitotic shortly after birth
○ Injury can severely handicap amitotic tissues
○ The cause of aging is unknown, but chemical and physical insults, as well as
genetic programming, have been proposed as possible causes
○ Neoplasms, both benign and cancerous, represent abnormal cell masses in
which normal controls on cell division are not working
○ Hyperplasia (increase in size) of a tissue or organ may occur when tissue is
strongly stimulated or irritated
○ Atrophy (decrease in size) of a tissue or organ occurs when the organ is no
longer stimulated normally
