Unit 2 – Part 2
Tissues
Tissues
• Tissues: a group of cells
with similar structure and
function
• Histology: the study of
tissues
• There are 4 primary types
of tissues:
–
–
–
–
Epithelium = covering
Connective = support
Muscle = movement
Nervous = control
Epithelial Tissue
• Found in:
– Body coverings
– Body linings
– Glands
• Function:
– Protection
– Absorption
– Filtration
– Secretion
Epithelial Tissues
• Characteristics:
– Cells fit closely together
– Tissue always has one free surface (apical
surface)
– Lower surface (basal surface) bound by a
basement membrane (network of
fibers/connective tissue)
– Regenerate easily
Classification of Epithelium
• Number of cell layers
– Simple: one layer
– Stratified: two or more
layers
– Pseudostratified:
uneven layers
Classification of Epithelium
• Shape of Cells
– Squamous: flattened
(squamous = thin, easily
removed)
– Cuboidal: cube-shaped
– Columnar: column-like
• Combinations of these terms
give us our specific Epithelium
types
Types of Epithelium
• Simple Squamous
– Description: Single layer
of flat cells
– Function: Usually forms
membranes that allow
diffusion and filtration
– Present in:
• Lining of body
cavities
• Lining of lungs and
capillaries
Types of Epithelium
• Simple Cuboidal
– Description: Single
layer of cube-like
cells
– Function: allow
secretion and
absorption
– Present in:
• Kidney tubules
• Ducts of glands
• Ovary surface
Types of Epithelium
• Simple Columnar
– Description: Single layer of
tall cells
• Many have cilia or
microvilli
• Will often have “goblet
cells” – secrete mucus
– Function: Absorption and
Secretion
– Present in:
• Digestive tract, gallbladder
• Ciliated: uterus, bronchi of
lungs
Types of Epithelium
• Pseudostratified
Columnar
– Description: Single layer of
cells with different heights
• Many have cilia or
microvilli
• Will often have “goblet
cells” – secrete mucus
– Function: secretion and
propulsion of mucus
– Present in:
• Sperm-carrying ducts
• Trachea
Types of Epithelium
• Stratified Squamous
– Description: Layers of
cells, cells at the free
edge are flattened
– Function: Protection of
underlying areas where
friction is common
– Present in:
• Skin
• Mouth
• Esophagus
Types of Epithelium
• Stratified Cuboidal*
– Rare in the body, typically 2 cell-layers thick,
found in some sweat and mammary glands
• Stratified Columnar*
– Limited distribution in the body; surface cells
are columnar, and cells underneath vary in
size and shape; occurs at transition areas
between 2 types of epithelium
*Won’t need to identify picture
Types of Epithelium
• Transitional
Epithelium*
– Description:
combination of types
of cells
– Function: stretching
– Present in: bladder
*Won’t need to identify picture
Types of Epithelium
• Glandular*
– Gland: one or more cells that make and secrete a
particular product
– Two major gland types:
• Endocrine gland
– Ductless
– Secretions are hormones
• Exocrine gland
– Empty through ducts onto body surfaces (skin)
or into body cavities
– Secretions are sweat and oil
– More numerous than endocrine
*Won’t need to identify picture
Connective Tissue
• Found in:
– All areas of the body
– Most abundant type of tissue!
• Function:
– Binds body tissues together
– Supports body
– Provides protection
Connective Tissue
• Characteristics:
– Underlies epithelium
– The cells are in a fiber MATRIX – there’s lots
of non-living material that surrounds the living
cells
– Types include Bone, Cartilage, Dense
Connective, Loose Connective, and Blood
Types of Connective Tissue
• Bone
– Description:
• Bone cells in cavities
• Hard matrix of calcium
salts
• Large amount of
collagen fibers
– Function: used to protect
and support the body
Types of Connective Tissue
• Cartilage:
– Three types…
• Hyaline cartilage
– Keeps bones from rubbing
together
– Has abundant collagen fibers
and a rubbery matrix
– Most common cartilage
– Entire fetal skeleton is hyaline
cartilage
– Found at end of long bones, rib
cartilage, trachea, nose
Types of Connective Tissue
• Elastic Cartilage
– Provides elasticity
– EX: external ear, epiglottis
• Fibrocartilage
– Highly compressible
– EX: cushion disks between vertebrae, pubic
symphysis, knee joint discs
Types of Connective Tissue
• Dense (Fibrous)
Connective
– Description:
Contains LOTS of
collagen fibers
– EX: Tendons
(attach muscle to
bone) and
Ligaments (attach
bone to bone)
Types of Connective Tissue
• Loose Connective
– Areolar
• Soft, pliable
• Usually found under
epithelium
– Reticular
• Interwoven fibers that
support lots of cells
• Found in lymph nodes,
spleen, and bone
marrow
Types of Connective Tissue
• Blood
– Surrounded by fluid
matrix (plasma)
– Functions as the
transport vehicle for
materials (gases,
nutrients, wastes, etc.)
– Includes erythrocytes
(Red Blood Cells) and
Leukocytes (White
Blood Cells)
Muscle Tissue
• Found in: Muscles! DUH!
• Function: Produce movement
• Characteristics:
– Properties include elasticity and contractility
– Three types…
Muscle Tissue Types
• Skeletal Muscle
– Description:
• Cells are striated
• Cells have more
than one nucleus
• Cells attach to
connective tissue
– Function:
• Voluntary control of
muscles
Muscle Tissue Types
• Cardiac Muscle
– Description:
• Cells are striated
• Cells have one nucleus
• Cells attached to other
cardiac muscles
• Has Intercalated disks
– Function:
• Pump blood
involuntary
Muscle Tissue Types
• Smooth Muscle
– Description:
• Cells are not striated
• Cells have one nucleus
• Cells attach to other
smooth muscle cells
– Function:
• Surround hollow organs
• Function involuntarily
Nervous Tissue
• Found in: Brain, Spinal Cord, Nerves
• Function: Send and receive impulses from
other areas of the body
Motor Unit! (Includes Muscle)
Tissue Repair
• Can happen two ways…
– Regeneration: replacement of destroyed
tissue by the same kind of cells
– Fibrosis: repair by dense fibrous connective
tissue (scar tissue)
• Type of repair determined by type of tissue
damaged, and by severity of the injury
Tissue Repair
• Tissues that regenerate easily:
– Epithelial Tissue
– Fibrous Connective Tissue & Bone
• Tissues that regenerate poorly:
– Skeletal Muscle Tissue
• Tissues mainly replaced with scar tissue:
– Cardiac Muscle Tissue
– Nervous Tissue within brain & spinal cord