Download Tissues- A group of similar cells that perform a common function.

Tissues- A group of
similar cells that
perform a common
function.
Ch. 5
Types of Tissues
• Epithelial- covers & protects the body
surface, lines body cavities, moves
substances in & out of blood, and forms
many glands.
• Connective Tissue- Supports body, holds
body parts together, transports substances
through the body & protects it from foreign
invaders.
Embryonic Development of
Tissues
• After fertilization, the cell divides and becomes a
hollow ball of cells called a blastocyst. These
cells regroup and form the three primary layers
(gastrulation):
–
–
–

Endoderm
Mesoderm
Ectoderm
These layers then differentiate into tissues
(histogenesis)
Functions of Epithelial Tissue
• Protection- from injury & foreign particles
• Sensory- found in skin, nose, eye & ear
• Secretion- include hormone, mucus,
digestive juices & sweat.
• Absorption- of nutrients & gases in lungs
• Excretion- kidney & urine
Classification Based on Cell
Shape
• Four cell shapes:
–
–
–
–
squamous: flat & platelike
cuboidal: cube-shaped
columnar: narrow & cylindrical
pseudostratified columnar: oddly shaped with
some nuclei near the top & some near the
bottom of the cell
(Figure 5-2)
Classification Based on Layers
of Cells
• Simple- cells arranged in a single layer
• Stratified- cells layered one on another
• Transitional- differing cell shapes in a
stratified or layered sheet
(Figure 5-2)
Simple Squamous Epithelium
• One layer of flat, scalelike cells.
• Substances can readily diffuse or filter
through.
• Examples include the microscopic air sacs
(alveoli) in the lungs & lining of blood
vessels)
(Figure 5-5)
Simple Cuboidal Epithelium
• One layer of cuboidal cells
• Found in many types of glands & ducts.
• Also found in organs, such as the kidney.
Simple Columnar Epithelium
• Lines the stomach, intestine, uterus, uterine
tubes, and parts of the respiratory tract.
• Because these cells are larger they offer
more protection while still allowing
secretion/absorption to take place.
Pseudostratified Columnar
Epithelium
• Found lining the air passages of the
respiratory system & certain segments of the
male reproductive system such as the urethra.
• Cells are of differing heights
Stratified Squamous Epithelium
• Multiple layers of flat cells
• Some are composed of keratin (helps protect
& waterproof) & are found in the skin
• Others are nonkeratinized and are found in the
vagina, mouth & esophagus
Stratified Cuboidal Epithelium
• Generally serves as protection
• Located in sweat gland ducts, in the
pharynx & over parts of the epiglottis
Stratified Columnar Epithelium
• Not common in the body
• Found only in parts of the male urethra &
in the mucous layer near the anus
Stratified Transitional
Epithelium
• Has the ability to stretch & flatten out
• Found in the walls of the bladder
• Protects the bladder wall from tearing when
stretched
Exocrine Glands- discharge their
secretions into ducts
Endocrine Glands- discharge
their secretions directly into
the blood
Types of Exocrine Glands
• Apocrine glands- Milk producing
Ex. mammary glands
• Holocrine glands- produce oil to lubricate
the skin
• Merocrine glands- Salivary glands
Connective Tissue
• Connective tissue connects, supports, transports
and defends.
• Connects tissue to tissue, muscle to muscle, bone
to muscle and bones to bones.
• Blood is a connective tissue that transports
substances between parts of the body
• Other connective tissue cells defend us against
microorganisms & invaders
Loose Connective Tissue
• Stretchable & widely distributed around
the body
• Not as specialized as other connective
tissue
Adipose Tissue
• Forms a protective barrier around the
kidneys & other various structures
• Storage for excess food
• Insulates the body to conserve heat
Reticular Tissue
• Forms the framework of the spleen, lymph
nodes & bone marrow.
• Helps defend the body against foreign
substances
Dense Fibrous Tissue
• Is flexible but very strong
• Tendons & ligaments are made of this
• Forms the strong inner skin layer called the
dermis
• Also forms the outer layer of organs like
the kidney & the spleen