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Tissues
Chapter 5
Tissues
• A tissue is a group of similar cells that are
specialized for a particular function.
• Histology – the study of tissues
The Immortal Life of Henrietta Lacks
Four Principal Types of Tissues:
• Epithelial –covering and lining; glands
• Connective – protects and supports, binds
organs together, stores energy, and
provides immunity
• Muscle – movement
• Nervous –transmits impulses that
coordinate body activities
Epithelial Tissue Characteristics
• Closely packed cells with little extracellular
material between cells
• Epithelial cells are arranged in continuous
sheets, in single or multiple layers
Epithelial Tissue Characteristics
• Avascular, meaning no blood vessels.
• Attached firmly to nearby connective tissue
by means of the basement membrane .
• Has a good nerve supply
Epithelial Tissue Characteristics
• Constant cell division since it is subject to
wear and tear.
• Epithelial tissue functions include:
protection, filtration, secretion, absorption,
excretion, transportation
**Epithelium is named for its cell shape
and number of layers
Covering and Lining Epithelium
Epithelial layers are arranged as:
• Simple epithelium (one layer)
•
•
Stratified epithelium (several layers)
Pseudostratified epithelium (one layer that
looks like several)
nuclei at different level; not all cells reach the
surface***
*** cells that do have cilia or secrete mucus.
Number of
Layers
Simple
Stratified
Pseudostratified
Transitional*
Cell Shapes
• Squamous (flat) for diffusion
• Cuboidal (cubelike) - produce secretions and
function in absorption
• Columnar (rectangular) - protect underlying
tissue, may have cilia, secretion or absorption.
• Transitional (variable) - change in shape from flat
to columnar due to distention, expansion or
movement of body parts.
Cell Shapes
Classification is by number of layers and
cell shape (top layer)
• Simple squamous epithelium • 1. single layer of flat cells.
• 2. found in heart, blood vessels, lungs, and
kidneys.
• 3. Diffusion, osmosis, and filtration
Classification is by number of layers and
cell shape (top layer)
• Simple cuboidal epithelium • 1. single layer of cube-shaped cells.
• 2. found in ovaries, glands, and kidneys
• 3. secretion and absorption
***(cuboidal - think glands!)
Classification is by number of layers
and cell shape (top layer)
• Simple columnar epithelium comes in two
forms: with or without cilia
• Simple columnar epithelium • 1. a single layer
• 2. lines the digestive tract from the
stomach to the anus
Classification is by number of layers
and cell shape (top layer)
• 3. Functions - secretion, absorption, protection,
and movement
• 4. Special feature - can have cilia and Goblet cells
that secrete mucus
Classification is by number of layers
and cell shape (top layer)
• Pseudostratified columnar epithelium
• 1. Has only one layer but looks like it has many layers. (Some
cells do not reach the surface.)
• 2. Lines passages of respiratory system
• 3. Functions - secretion and movement
• 4. Pseudostratified ciliated - has cilia and goblet cells
Stratified Epithelial Tissue
• Has at least two layers of cells. Named by shape
of the cells in the superficial layer.
• Stratified squamous epithelium –
• 1. several layers of cells (Top layer has flattened cells.)
• 2. Found in skin, mouth, vagina, and throat
• 3. Function - protection
• 4. keratin - protein found in outer layer of skin.
Waterproofs skin
Stratified Epithelial Tissue
• Stratified cuboidal epithelium • 1. consists of several layers
(Top layer is cube-shaped)
• 2. Found in ducts of glands
(sweat, mammary, etc)
• 3. Function is mainly protection.
• 4. Fairly rare
Stratified Epithelial Tissue
• Stratified columnar epithelium • 1. several layers of cells (Top layer is rectangular.)
• 2. Found in male vas deferens & urethra, pharynx
• 3. Functions in protection & secretion
• 4. Also uncommon
Stratified Epithelial Tissue
• Transitional epithelium
• 1. Has many layers
• 2. Found in the urinary bladder & urethra
• 3. Function - expansion or stretching (distention)
Glandular Epithelium
• A gland is a single cell or a mass of epithelial
cells adapted for secretion.
• There are two types depending on how the
cells release the substances they produce:
exocrine glands and endocrine glands
Glandular Epithelium
OUT
OUT OF
INTO
Glandular Epithelium
• Exocrine glands secrete product out of ducts
or directly onto a free surface.
• Secretions include mucus, sweat, oil, ear wax,
saliva, and digestive enzymes.
Glandular Epithelium
Classification of exocrine glands :
Holocrine - whole cell disintegrates
(example - sebaceous glands)
Apocrine glands - a portion of cell pinched off.
Cell repairs itself.
(example - mammary glands)
Merocrine - substance secreted by going through
cell membrane (exocytosis).
(example - salivary glands)
Glandular Epithelium
• Endocrine glands - “ductless glands”
• discharge their secretions into the
bloodstream.
• secretions - hormones, which regulate many
bodily functions.