body tissues
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Body Tissues. Ch.3 (Part II). Body Tissues. Cells are specialized for particular functions Tissues Groups of cells with similar structure and function Four primary types Epithelium Connective tissue Nervous tissue Muscle. Body Tissues. - PowerPoint PPT PresentationTRANSCRIPT
Body TissuesCh.3 (Part II)
Body Tissues Cells are specialized for particular functions Tissues
Groups of cells with similar structure and function
Four primary types Epithelium Connective tissue Nervous tissue Muscle
Body Tissues If we had to assign a single term to each primary
tissue type that would best describe its overall role, the terms would most likely be:
Covering (epithelium) Support (connective) Movement (muscle) Control (nervous)
However, these terms only reflect only a tiny fraction of the functions that each of these tissues perform.
1. Epithelial TissuesFound in different areas
Body coverings Body liningsGlandular tissue (forms glands in
body)
FunctionsProtectionAbsorptionFiltrationSecretion
Special Characteristics of Epithelium: Cells fit closely together (except for glandular) to
form connective sheets Tissue layer always has one free surface. This so
called “apical surface” is exposed to the body’s exterior or to the cavity of an internal organ.
The lower surface of epithelium is bound by a basement membrane (a structure less material secreted by cells)
Avascular (have no blood supply) so they depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen
Regenerate easily if well nourished
Classification of Epithelium
1. Number of cell layers
Simple – one layer
Stratified – more than one layer
Figure 3.17a
Classification of Epithelium
2. Shape of cells Squamous – flattened
(like fish scales)
Cuboidal – cube-shaped (like dice)
Columnar – column-like (like columns…duh)
Figure 3.17b
Simple or Stratified…Simple
One layer of cells Most concerned with
absorption, secretion, and filtration
Because they are usually very thin, protection is not one of their specialties
Stratified Consist of two or
more cell layers More durable than
the simple epithelia
Function primarily to protect
Simple Epithelium 1. Simple squamous
Single layer of flat cells Usually forms membranes
where filtration or exchange of substances by rapid diffusion occurs. Lines body cavities Lines lungs and capillaries
Figure 3.18a
Simple Epithelium 2. Simple cuboidal
Single layer of cube-like cells
Common in glands and their ducts
Forms walls of kidney tubules
Covers the ovaries
Figure 3.18b
Simple Epithelium
3. Simple columnar Single layer of tall cells Often includes goblet
cells, which produce mucus
Lines the entire digestive tract from the stomach to the anus
Figure 3.18c
Simple Epithelium 4. Pseudostratified
Single layer, but some cells are shorter than others
Often looks like a double cell layer (false…hence the name pseudo)
Sometimes ciliated, such as in the respiratory tract
May function in absorption or secretion Figure 3.18d
Stratified Epithelium 1. Stratified squamous
Cells at the free edge are flattened but closer to the basement membrane, are cuboidal or columnar
Found as a protective covering where friction/abuse is common
Locations Skin Mouth Esophagus
Figure 3.18e
Stratified Epithelium 2. Stratified cuboidal
Two layers of cuboidal cells 3. Stratified columnar
Surface cells are columnar, cells underneath vary in size and shape
Stratified cuboidal and columnar Rare in human body Found mainly in ducts of large glands
Stratified Epithelium 4. Transitional epithelium
Shape of cells depends upon the amount of stretching (near basement: typically columnar or cuboidal, at surface: varies)
Lines organs of the urinary system like the bladder, ureters, and part of the urethra where considerable amounts of stretching occur.
Figure 3.18f
Glandular Epithelium Gland – one or more cells that secretes a particular
product (secretion)
Two major gland types develop from epithelial sheets:
1. Endocrine gland Ductless (hormones diffuse directly into the blood vessels that
weave through the glands) Secretions are all hormones Examples of endocrine glands: thyroid, adrenals, and pituitary
2. Exocrine gland Empty through ducts to the epithelial surface Include sweat and oil glands, and liver and pancreas Are both internal and external
Connective Tissue Found everywhere in the body &
connects body parts Includes the most abundant and widely
distributed tissues Functions
Binds body tissues together Supports the body Provides protection
Connective Tissue Characteristics:
Variations in blood supply Some connective tissue types are well vascularized
(good blood supply) Some have poor blood supply or are avascular like
tendons and cartilages (these things heal slowly) Extracellular matrix
Connective tissues are made up of many different types of cells plus varying amounts of non-living material that surrounds living cells (called the extracellular matrix)
Extracellular MatrixMakes connective tissue different from any other
tissue.
Two main elements Ground substance – mostly water
along with adhesion proteins and polysaccharide molecules
FibersProduced by the cellsThree types
Collagen fibersElastic fibersReticular fibers
Extracellular Matrix Continued:
Allows connective tissue to form a soft packaging tissue around
other organs, to bear weight, and to withstand stretching and other
abuses, such as abrasionthat no other tissue could endure.
Connective Tissue Types: Bone (osseous tissue)
Composed of:Bone cells in lacunae
(cavities)Surrounded by a hard
matrix of calcium saltsLarge numbers of
collagen fibers Because of its
rocklike hardness, bone is used to protect and support the body Figure 3.19a
Connective Tissue Types:
Hyaline cartilage Most common cartilage
(cartilage is found only in a few places in the body…is less hard and more flexible than bone.)
Composed of: Abundant collagen fibers Rubbery matrix Blue-white appearance
Entire fetal skeleton is hyaline cartilage (turns to bone by birth)!
Also forms the supporting structure of the larynx (voicebox), attaches ribs to the breastbone, and covers the ends of bones where they form joints.
Figure 3.19b
Connective Tissue Types: Elastic cartilage
Provides elasticity Example: supports the external ear
Connective Tissue Types:
Fibrocartilage Highly compressible Example: forms
cushion-like discs between vertebrae
Figure 3.19c
Connective Tissue Types: Dense connective tissue
Main matrix element is collagen fibers
Cells are fibroblasts (fiber forming cells)
Forms strong ropelike structures (like the examples listed below)
Examples Tendon – attach muscle to
bone Ligaments – attach bone to
boneFigure 3.19d
Connective Tissue Types: Areolar connective
tissue Most widely distributed
connective tissue Soft, pliable
“cobwebby” tissue that cushions and protects the body organs
Helps hold internal organs together and in their proper positions
Contains all fiber types Can soak up excess
fluid Figure 3.19e
Figure 3.19f
Connective Tissue Types: Adipose tissue:
Commonly called fat! Matrix is an areolar
tissue in which fat cells predominate
Many cells contain large lipid deposits
Functions Insulates the bodyProtects some organsServes as a site of
fuel storage
Connective Tissue Types:Reticular connective
tissueDelicate network of
interwoven fibersForms stroma
(internal supporting network) of lymphoid organsLymph nodesSpleenBone marrow
Figure 3.19g
Connective Tissue Types: Blood (vascular tissue)
Blood cells surrounded by fluid matrix (called plasma)
Fibers are visible during clotting
Functions as the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, and many other substances throughout the body. Figure 3.19h
Muscle Tissue Function is to produce movement Three types
1. Skeletal muscle2. Cardiac muscle3. Smooth muscle
Muscle Tissue Types: 1. Skeletal muscle
Can be controlled voluntarily
Form the muscular system
Cells attach to connective tissue
Cells are striated (striped)
Cells have more than one nucleus
Figure 3.20a
Muscle Tissue Types 2. Cardiac muscle
Found only in the heart Function is to pump blood
(involuntary) Cells attached to other
cardiac muscle cells at intercalated disks (have gap junctions …remember this mean info can pass freely from cell to cell….)
Cells are striated One nucleus per cell Under involuntary control
Figure 3.20b
Muscle Tissue Types 3. Smooth muscle
AKA: visceral muscle Involuntary muscle Surrounds hollow
organs Spindle-shaped
(pointed at each end) Attached to other
smooth muscle cells No visible striations
(hence the name smooth)
One nucleus per cellFigure 3.20c
Nervous Tissue Neurons and nerve
support cells Function is to send
impulses to other areas of the body Irritability Conductivity
Figure 3.21
Tissue Repair (Wound Healing)
Tissue repair occurs in two major ways…
1. Regeneration Replacement of destroyed tissue by the same kind of
cells 2. Fibrosis
Repair by dense fibrous connective tissue (scar tissue is formed)
Determination of method Type of tissue damaged Severity of the injury
Tissue injury sets a series of events into motion…
1. Capillaries become very permeableA. Introduce clotting proteinsB. Wall off injured area
2. Formation of granulation tissue3. Regeneration of surface epithelium
Regeneration of Tissues
Tissues that regenerate easily Epithelial tissue Fibrous connective tissue and bone
Tissues that regenerate poorly Skeletal muscle
Tissues that are replaced largely with scar tissue Cardiac muscle Nervous tissue within the brain and spinal cord
Read about Homeostatic Imbalance on pg. 98 and make notes….