5-1
CHAPTER 5
TISSUES
I. GENERAL INFORMATION
A.
Tissues are made of groups of cells with similar structure and function.
B.
Cells can be tightly packed or separated by interstitial material.
C.
D.
4 Primary Tissues
1.
Epithelial
2.
Connective
3.
Muscle
4.
Nerve
Tissues are building blocks for the body’s organs.
II. EPITHELIAL TISSUES
A.
General Characteristics
1.
Locations:
• Line internal body cavities
• Cover the body’s surface
• Make up glands
• Cover organs
2.
Cells closely packed
3.
Avascular (no blood vessels)
• Receive nutrition and remove waste by diffusion from underlying tissues
4.
Cells replaced at a rapid rate
5.
Always have a free surface
• Anchored to underlying connective tissue by a thin, nonliving basement membrane
composes of 2 layers:
a.
basal lamina
b.
reticular fibers
6.
B.
Functions:
• Protective barrier
• Secretion
• Absorption
• Excretion
• Sensory reception
• Protection
• Diffusion
Classification of Epithelium
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1.
2.
By Cell Shape
a. Squamous--flattened
b.
Cuboidal—cube-shaped
-equal in height and width
c.
Columnar—cells taller than are wide
By Cell Arrangement
a. Simple—single layer of cells
b.
Stratified—many layers thick
c.
Pseudostratified—“false stratification”
-appears to be layered but is not
d.
C.
Transitional—several layers of soft, easily stretched cells which are flattened
when stretched, but change form when relaxed
-Ex: empty bladder
Types of Epithelium and Their Functions
1.
Simple Squamous
a. Single layer of flat, thin irregular cells
b.
Line blood vessels, heart, lungs—anywhere diffusion must occur
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c.
Functions:
• Secretes serous (watery) fluid to reduce friction between membranes
• Allows for diffusion
2.
Stratified Squamous
a. Made of several layers of flattened cells
b. Cover the body and line openings into the body (mouth, vagina, anus)
c.
Cover some internal organs
d.
Outermost layer may have protoplasm replaced by keratin (protein) for added
protection against drying and invasion
• Dead cells
e.
Function:
• Protection
3.
Simple Cuboidal
a. Equal in height and width
• Centrally located nuclei
• One layer
b.
Cover ovaries, line kidney tubules, and line ducts of glands
c.
Function:
• Secretion
• Absorption
4.
Simple Columnar
a. Tall cells closely packed, with nuclei near the basement membrane
• One layer
b.
c.
Line digestive tract and uterus
Functions:
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d.
• Protection
• Secretion of mucus, enzymes
• Absorption
Have tiny microvilli which increase surface area
e.
Have goblet cells which secrete mucus
5.
Pseudostratified Columnar
a. Appeared layered but are not
b. Often with cilia and goblet cells (secrete mucus)
c. Line respiratory passages and reproductive system tubes and the uterus
d. Function:
• Aids in movement of cells and substances
6.
Transitional
a. Undergoes changes in tension
b. Lines the bladder
c. Function:
• Protection
• Stretching
d. Cuboidal cells
Glandular Epithelium
a. Composed of cells which secrete substances
b. Columnar or cuboidal
c. 2 types of glands:
• Exocrine—secrete substances into ducts, onto internal or external surfaces
• Endocrine—secrete substances into tissue fluid or blood
--ductless
d. Exocrine Gland Classification:
1. Merocrine
• Fluid cellular product released through cell membrane (serous or
mucous)
2. Apocrine
• Lose small portions of cells during secretion
3. Holocrine
7.
5-5
•
Release entire cells filled with secretory products
III. CONNECTIVE TISSUE
A. General Characteristics
1. Occurs in all parts of the body
2. Functions:
• Bind
• Support
• Fill spaces
• Store fat
• Produce blood cells
• Protect
• Help repair tissue damage
3. Vascular (with the exception of cartilage)
4. Regenerates slower than epithelium
5. Have matrix between cells
6.
Some flexible—loose, adipose, dense
7.
Some rigid—bone and cartilage
8.
Composed of 3 components:
a. Cells
• Wandering cells—white blood cells
• Fixed cells
cFibroblasts
-most common
-large, star-shaped
-secrete proteins into the matrix to form fibers
dMacrophages
-phagocytic
eMast cells
-located near blood vessels
-contain heparin to prevent clotting and histamine that promotes allergic
reactions
b.
Ground Substance (Matrix)
• Protein-polysaccharide complex which maybe liquid, solid, or gel
c.
Fibers
cCollagenous
-most common fiber
-composed of protein collagen
-produced by fibroblasts
-white
-form bundles
-Function: give strength
Ex: tendons (join muscle to bone)
dElastic
-Yellow
-Produced by fibroblasts
-Allow tissue to stretch
-Not as strong as collagenous
-important in large arteries and in vocal cords
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-made of protein elastin
eReticular
-very thin
-composed of collagen
-form delicate supporting networks
B. Types of Connective Tissue and Their Function
1. Mesenchyme
• Embryonic connective tissue
• Gives rise to all other connective tissues
2. Loose Connective Tissue
• Cells and fibers widely scattered in the matrix
• Cells mainly fibroblast, collagenous and elastic fibers
• Filler tissue
• Contains numerous blood vessels that provide nourishment for epithelial cells
3. Adipose Tissue
• “Fat,” specialized form of loose connective tissue that stores fat
• Lipocyte—fat cell
• Functions:
- reserve energy supply
- protects body from jolts
- insulates
4. Dense Connective Tissue (Fibrous)
• Elastic and collagenous fibers closely packed with few cells (mostly fibroblasts)
• Poor blood supply
• Ex: Tendons—connect muscles to bone
Ligaments—connect bones to bones at joints
• Functions:
-supports and binds joints together
5. Specialized Connective Tissues
a. Cartilage
• Functions:
-support
-framework
-protection
-models for bones
• Gel-like matrix embedded with fibers and cells (chondrocytes) in spaces called
lacunae
• Nonvascular; surrounded by a very vascular perichondrium
• 3 types:
cHyaline
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b.
-most common
-on ends of bones, nose, bronchi
-important in the development of bones
-composed of white fibers
dElastic
-composed of yellow fibers
-found in ears and part of larynx
eFibrocartilage
-composed of white fibers
-forms intervertebral discs between vertebrae and acts as a cushion
between bones in knee and pelvic girdle
Bone (osseous tissue)
• Most rigid connective tissue
• Develops by ossification from cartilage
• Hardness due to mineral salts in the matrix
• 2 types of cells allow for constant remodeling
costeoblasts—secrete matrix
dosteoclasts—tear down and reabsorb bone
• Bone is made up of cylinder-shaped units called Haversian Systems or
osteons.
-Matrix deposited in thin layers (lamellae) arranged in concentric layers
around tube (blood vessels) called Haversian Canals
-Lacunae which contain osteocytes (bone cells) are located in the lamellae
-Canaliculi—canals that connect lacunae
Functions:
-support
-protection
-produce blood cells
-attachment for muscles
-store inorganic salts
Blood
• Fluid tissue which carries nutrients and removes waste
• Made of fluid matrix (plasma)
• 3 cell types:
-erythrocytes
-leukocytes
-thrombocytes
Dentin
• Found in teeth
•
c.
d.
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e.
• Similar to bone
• Covered with enamel
Reticuloendothelial Tissue
• Variety of cells specialized as phagocytes
• In blood, lungs, brain, bone marrow, and lymph glands
• Help defend against infection
IV. NERVE TISSUE
A. Located in the brain, spinal cord, and peripheral nerves
B. Cannot be replaced once damaged
C. 2 main cell types:
1. Neurons
• Conducting cells
2. Neuroglial Cells
• Support and bind nerve tissue together
• Phagocytic in some cases; nutritive in others
V. MUSCLE TISSUE
A. Skeletal Muscle (Striated)
1. Voluntary
2. Striated
3. Multinucleated
4. Function: movement of bones
B. Smooth Muscle (Visceral)
1. Involuntary
2. No striations
3. One nucleus
4. Located in walls of organs or digestive system, arteries and veins
5. Function: controls movement of internal organs
C. Cardiac Muscle
1. Located only in the heart
2.
Striated
3.
Involuntary
4. Branched
5. One nucleus
6. Function: controls beating of the heart