Download Unit 2: Tissues

TISSUE TYPES
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Tissue refers to a group of cells that work together in the body.
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The cells of a tissue share:
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An embryonic origin.
Morphological features.
Arranged in an orderly pattern to perform their function.
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Four broad categories of tissues: epithelial, connective, muscle, and nervous.
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The cell types are characterized by specific functions that contribute to the overall
health and maintenance of the body.
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A disruption of the structure of a tissue is a sign of injury or disease.
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Histology - the microscopic study of tissue appearance, organization, and function.
EMBRYONIC ORIGIN
• The zygote, or fertilized egg, is a single cell formed by the fusion of an egg
and sperm.
• After fertilization the zygote goes through many rapid mitotic cycles,
forming an embryo.
• The first embryonic cells are totipotent meaning they have the ability to
differentiate into any type of cell in the body.
• There are three major cell lineages established within the embryo.
• Each forms the distinct germ layers from which all the tissues and organs
of the human body eventually form.
• Three germ layers identified by their relative position:
• ectoderm (ecto- = “outer”)
• mesoderm (meso- = “middle”)
• endoderm (endo- = “inner”).
FOUR TYPES OF TISSUE
• Epithelial tissue (epithelium) - sheets of cells that cover exterior
surfaces of the body, lines internal cavities and passageways, and
forms certain glands.
• Connective tissue - binds the cells and organs of the body together
and functions in the protection, support, and integration of all parts of
the body.
• Muscle tissue - excitable, responding to stimulation and contracting
to provide movement. Three major types: skeletal (voluntary) muscle,
smooth muscle, and cardiac muscle in the heart.
• Nervous tissue - excitable, allowing the propagation of
electrochemical signals in the form of nerve impulses that
communicate between different regions of the body.
EPITHELIAL TISSUE
*Naming is based on
description*
simple = single layer
stratified = multiple layers
squamous = flat
cuboidal = square
columnar = column (rectangle)
The cells are arranged in different forms, each form has a
different function.
SIMPLE
SQUAMOUS
Simple Squamous
Tissue
Form: Flat and thin
Function: diffusion and filtration. Air sacs in lungs, capillaries
STRATIFIED SQUAMOUS
Multi layer squamous,
functions in
protection
Found lining body
cavities; skin and
mouth
SIMPLE CUBOIDAL
Function: Secretion
and absorption
Found in kidneys
tubules, ducts and
covering the ovaries
SIMPLE COLUMNAR
Function: Secretion
and absorption
Found in digestive
tract and uterus
*Contains scattered
goblet cells to secrete
mucus
*Can have microvilli
PSEUDOSTRATIFIED COLUMNAR
Appear stratified, but just a single layer
of cells, nuclei at different levels
Can have cilia (hair-like projections)
And goblet cells, which secrete mucus
Function: Secretion and
cilia-aided movement
Location: lining air passages
and tubes of the
reproductive system
TRANSITIONAL EPITHELIUM
Stretchable
Blocks diffusion (no leaking)
Found in the urinary bladder
GLANDULAR EPITHELIUM
Cells are specialized to
secrete substances
They make up the GLANDS
exocrine glands
Examples:
salivary, sweat
endocrine glands
hormones
Loose Connective Tissue
Binds underlying
organs to skin
and to each other
Forms delicate
thin membranes
throughout the
body
ADIPOSE TISSUE (FAT)
Energy Storage
FIBROUS CONNECTIVE TISSUE
Tendons =
muscles to bones
Ligaments =
bones to bones
HYALINE CARTILAGE
Location: covers ends of joints, nose and respiratory
passages, serves as padding
ELASTIC CARTILAGE
Location: External Ear and Larynx
FIBROCARTILAGE
Tough, shock absorbing
Location: Between vertebrae
BONE TISSUE (OSSEUS)
BLOOD TISSUE
CARDIAC MUSCLE
SKELETAL MUSCLE
(STRIATED)
SMOOTH MUSCLE
NERVE TISSUE
ORGANS
• Several types of tissues come together to form a working unit,
an organ.
• Knowledge of tissues will help you understand how organs
function.