Download Tissue and Skin

Tissue and Skin
Tissues
• Tissues are layers or groups of similar
cells with a common function
• 4 types of tissues include:
• Epithelial
• Connective
• Muscle
• Nervous
Epithelial Tissue
• Epithelial tissue covers all free body surfaces,
forms the inner lining of body cavities, lines
hollow organs, and is the major tissue of
glands.
• A basement membrane anchors epithelium to
connective tissue. Epithelial tissue lacks blood
vessels, has cells that are tightly packed, and is
continuously replaced.
• It functions in protection, secretion,
absorption, and excretion.
Epithelial Tissue
Apical Surface
Basal Surface
• A free surface or
edge exposed to
the body’s exterior
or to the
cavity/lumen of an
internal organ.
• Basement
membrane
• Lower surface of
epithelium
• Structureless
material secreted
by the cells.
Types of Epithelial Tissue
Simple
• Squamous
• Cuboidal
• Columnar
• Pseudostratified
Stratified
• Squamous
• Cuboidal
• Columnar
• Transitional
Simple Squamous Epithelial
• This tissue consists of a
single layer of thin,
flattened cells through
which substances pass
easily.
• It functions in the
exchange of gases in
the lungs and lines
blood vessels, lymph
vessels, and
membranes within the
thorax and abdomen.
Simple Cuboidal Epithelium
• This tissue consists of
a single layer of cube
shaped cells.
• It carries on secretion
and absorption in the
kidneys and various
glands.
Simple Columnar Epithelium
• This tissue is
composed of
elongated cells
whose nuclei are
near the basement
membrane.
• It lines the uterus
and digestive tract,
where it functions in
protection, secretion
and absorption.
Pseudostratified Columnar
• This tissue appears
stratified because the
nuclei are at two or
more levels.
• Its cells may have
cilia that move
mucus over the
surface of the tissue.
• It lines tubes if the
respiratory system.
Stratified Squamous Epithelium
• This tissue is
composed of many
layers of cells; the top
layers are flattened.
• It protects underlying
cells from harmful
environmental effects.
• It covers the skin and
lines the oral cavity,
esophagus, vagina and
anal canal.
Stratified Cuboidal Epithelium
• This tissue is
composed of two or
three layers of cubeshaped cells.
• It lines the larger
ducts of the sweat
gland, salivary glands
and pancreas.
• It functions in
protection.
Stratified Columnar Epithelium
• The top layer of cells
in this tissue contains
elongated columns.
Cube-shaped cells
make up the bottom
layers.
• It is in part of the male
urethra and parts of
the pharynx
• Functions in protection
and secretion.
Transitional Epithelium
• Specialized to
become distended.
• It is in the walls of
organs of the urinary
tract.
• It helps prevent the
contents of the
urinary passageways
from diffusing out.
Connective Tissue
• Connects, supports, protects, fills spaces, stores
fat, produces blood cells, protects against
infections, and helps repair damage tissues
• Most are well vascularized except tendons,
ligaments and cartilage
• Fibers—made by CT cells and secreted
• Collagen fibers (white)
• Elastic fibers (yellow)
• Reticular fibers (fine collagen)
Types of Connective tissue
• From most rigid to softest:
• Bone
• Cartilage
• Dense connective tissue
• Loose connective tissue
• Blood
Major Cell types
• Fibroblasts produce collagenous and
elastic fibers
• Macrophages are phagocytes
• Mass cells release heparin and
histamine and usually are near blood
vessels
Bone
• The extracellular matrix of bone contains mineral salts and
collagen
• Its cells usually form concentric circles around osteonic canals
• Active tissue that heals rapidly
• Osseus tissue
• Most rigid connective tissue, with deposits of mineral salts
and collagen within the matrix.
• Bone cells, called osteocytes, lie within lacunae and are
arranged in concentric circles
• Good blood supply, enabling rapid recovery after an injury.
• Rocklike hardness allows protection and support of other body
organs
Cartilage
• Provides a supportive
framework for
various structures.
• Cartilage cells
(chondrocytes) lie
within lacunae in the
gel-like fluid matrix.
Types of Cartilage
• Hyaline cartilage is white with abundant fine
collagen fibers, is found at the ends of bones,
and supports respiratory passages.
• Elastic cartilage, with elastic fibers, provides a
framework for the external ears and parts of the
larynx.
• Fibrocartilage is a tough tissue that provides a
shock-absorbing
function in intervertebral disks and in the knees
and pelvic girdle.
Dense Connective Tissue
• This tissue consists of
densely packed
collagenous fibers and
is very strong but lacks
a good blood supply.
• Fibroblasts—cells that
make fibers
• It is found as part of
tendons and ligaments.
Loose Connective Tissue
• This type of tissue forms
delicate, thin membranes
throughout the body that
bind body parts together.
• Fibroblasts are separated
by a gel-like ground
substance that contains
collagenous and elastic
fibers.
• It binds the skin to
underlying organs and fills
spaces within muscle.
Areolar Tissue
• Most widely
distributed
connective tissue in
the body
• Cusions and protects
body organs it wraps
• “Glue” that holds
internal organs
together
Adipose Tissue
• Fat storing
connective tissue
• Found beneath the
skin (insulates the
body), around joints,
padding the kidneys
and other internal
organs, and in certain
abdominal
membranes.
Reticular Connective Tissue
• Network of
interwoven reticular
fibers associated with
reticular cells
• Internal supporting
framework
Blood
• Blood is composed of
cells (red and white)
suspended in a fluid
matrix (plasma).
• It is formed in the
blood-forming
tissues inside red
bone marrow and
functions to
transport substances
throughout the body.
The Integumentary System
• The skin and its accessory
structures make up the
integumentary system.
• Five major functions
• Serving as a barrier against
infection and disease
• Helping to regulate body
temperature
• Removing waste products
from the body
• Providing protection
against Ultraviolet
radiation from the sun
• Producing vitamin D
Layers of Skin
• Epidermis
• Dermis
• Subcutaneous layer
• beneath dermis
• not part of skin
Subcutaneous Layer
• Hypodermis
• Loose Connective Tissue
• Adipose Tissue
• Major Blood Vessels
Epidermis
•
•
•
•
•
•
Layer of stratified squamos epithelium that lacks blood vessels
Thickest on Palms
Keratonized
Outermost Layer
Its layers are made of Mostly DEAD CELLS.
Most of the cells of the epidermis undergo rapid cell division
(MITOSIS).
• As new cells are produced, they push older cells to the surface
of the skin. The older cells become flattened, lose their
cellular contents and begin making KERATIN.
Dermis
• Composed of irregular dense connective tissue that binds the
epidermis to underlying layer
• Contains blood vessels
• Nerve tissue is scattered through the dermis