Download Tissue Types - Waterford Public Schools

Tissue Types
4 types of tissues:
One organ can have all 4 types of tissue in it
Epithelial
Where found? :
• Covers the surface of the body
(the outer skin)
• Covers the surface of organs
• Forms the inner lining of body cavities
• Lines hollow organs
• Compose glands
Purposes:
• protection- tightly packed to form a protective barrier
• secretion- form glandular tissues (hormones, mucus,
digestive enzymes, sweat)
• absorption- the digestive tracts and lungs absorb nutrients
and gases
• excretion- elimination of waste products- alveoli of lungs,
kidney tubules
• filtration- lines the kidney tubules which is where urine
products are filtered (pushed across the membrane) from
the blood
Characteristics
1. The Cells fit closely together to form sheets=
cells are connected by many intercellular junctions
Intercellular Junctions
• Tight junctions:
• Membranes between cells
merge and fuse
• Located among cells that form
linings, sheetlike layers
• Blood-brain barrier
• Desmosomes:
• Form “spot welds” between cells
• Structural reinforcement
• Located among outer skin cells
• Gap junctions:
• Tubular channels between cells
• Molecules can move between cells
• Located in cardiac muscle cells
Characteristics
2. The cells have Polarity=
cells have an apical (top) and basal (bottom) surface- each area is different in structure
and function
a. Apical surface- free and unattached (exposed to
body’s exterior or to a cavity)
1.) most have microvilli (increases surface area)lining intestines and kidney tubules
-brushed border= densely packed microvilli
2.) some contain cilia- lining of trachea= moves
substances along surface
3.) some smooth and slick
b. Basal surface- rests on a basement membrane which anchors
the epithelium to the underlying connective tissue
Upper (apical) surface is free and unattached
(exposed to body’s exterior or to a cavity)
The lower (basal) surface rests on a basement membrane
Microvilli and Cilia = epithelial
Brushed
border
Characteristics (cont’d)
3. Cells rest on a basement membranea supporting system under basal surface
• two parts:
a. basal lamina- next to basal (bottom) surfacethin, supporting, non-cellular, adhesive sheet
(made of glycoproteins)
1. acts as a selective filter for materials passing from the
lower connective tissue to the epithelial cells
2. provides a scaffolding for epithelium when the tissue is
repairing a wound
b. reticular lamina- contains collagen fibers that belong to
the underlying connective tissue
Cancer cells secrete a substance that
dissolves the basement membrane
allowing the cells to invade the underlying
tissue layers
Characteristics
4. avascular- lack blood vessels (relies on underlying tissue for food
and oxygen)
5. regenerates easily- so injuries heal quickly
- skin cells and the cells lining the stomach and intestines are
continually damaged
Classifications
Thin, flattened
By shape
cubelike
columnlike, elongated
1 layer
By number of layers
2 or more layers
Epithelial Tissue Types
Simple squamous:
•
•
•
•
•
•
Single layer of thin, flat cells
Substances pass easily through
Thin & delicate, can be damaged
Found in diffusion & filtration sites
Lines air sacs (alveoli) & capillaries
Lines blood & lymphatic vessels
Simple cuboidal:
• Single layer of cube-shaped cells
• Secretion and absorption
• Lines kidney tubules, thyroid
follicles
• Covers ovaries
• Lines ducts of some glands
15
Epithelial Tissue Types
Simple columnar:
• Single layer of elongated cells
• Nuclei usually at same level,
near basement membrane
• Sometimes have cilia
• Sometimes have microvilli
• Sometimes have goblet cells
(secrete mucus)
• Secretion and absorption
• Lines uterus, stomach, intestines
Pseudostratified columnar:
•
•
•
•
•
•
Single layer, but appears layered
Nuclei at 2 or more levels
Cells vary in shape
Often has cilia, goblet cells
Protection from infection
Lines respiratory passageways
16
Epithelial Tissue Types
Stratified squamous:
•
•
•
•
•
Many cell layers; thick
Protective layer
Outermost cells are flat
Deeper cells are cuboidal
New cells form, push older cells
toward free surface
• Outer layer of skin (keratinized)
• Lines oral cavity, vagina, anal canal
Stratified cuboidal:
• 2-3 layers of cube-shaped cells
• More protection than 1 layer
• Lines ducts of mammary, sweat,
& salivary glands, and pancreas
17
Epithelial Tissue Types
Stratified columnar:
• Top layer of elongated cells
• Cube-shaped cells in
deeper layers
• Lines part of male urethra,
ducts of exocrine glands
Transitional (uroepithelium):
• Many cell layers
• Cube-shaped and elongated
cells
• Changes shape with increased
tension; stretches
• Line urinary bladder, ureters,
and part of urethra
18
Glandular epithelium
• Composed of cells specialized to produce and secrete substances into
ducts or indo body fluids
a. exocrine- secrete into ducts
b. endocrine- ductless; secrete into body fluids (like the bloodstream)
2 structural types of exocrine glands:
a. Unicellular:
Composed of one cell, such as a goblet cell (secretes mucus)
b. Multicellular:
• Composed of many cells
• Sweat glands, salivary glands, etc.
• Simple or compound
Structural Types of Exocrine Glands
Simple: duct does not branch
Compound: duct branches before it reaches secretory portion
Tubular: consist of epithelial-lined tubes
Alveolar: terminal portions form saclike dilations
Types of Exocrine Glands
Types of Glandular Secretion
Merocrine Glands:
Secrete fluid products by exocytosis; salivary & sweat glands, pancreas
Apocrine Glands:
Lose small part of cell during secretion; mammary & ceruminous (wax)
glands
Holocrine Glands:
Release entire cells filled with product; sebaceous (oil )glands
Figure 4-6 Modes of Glandular Secretion.
(a) Merocrine secretion
In merocrine secretion, the product is released from secretory
vesicles at the apical surface of the gland cell by exocytosis.
Secretory
vesicle
Golgi
apparatus
Nucleus
TEM × 3039
Salivary gland
(b) Apocrine secretion
Mammary
gland
Apocrine secretion involves the loss of apical cytoplasm.
Inclusions, secretory vesicles, and other cytoplasmic components
are shed in the process. The gland cell then grows and repairs itself
before it releases additional secretions.
Breaks
down
Golgi apparatus
Secretion
Hair
1
2
Regrowth
3
4
Sebaceous gland
Hair follicle
(c) Holocrine secretion
Holocrine secretion occurs as superficial gland cells burst.
Continued secretion involves the replacement of these cells
through the mitotic divisions of underlying stem cells.
3 Cells burst, releasing
cytoplasmic contents
2
Cells form secretory
products and increase
in size
1 Cell division replaces
lost cells
Stem cell
Summary of Epithelial Tissues
24
Nervous Tissue
Where found?brain, spinal cord, peripheral nerves
Purpose
• Conduct impulses for coordination, regulation,
integration of body activities and sensory reception
Main cells are neurons, which are specialized for communication, via conduction of
nerve impulses (sensory reception, motor control)
Neuroglia support and nourish neurons