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PHYSIOLOGY

study of the function of the body
subdivisions based on organ systems(renal or cardiovascular)
often focuses on cellular and molecular level
body's abilities depend on chemical reactions in indicidual cells

TISSUE

Individual body cells specialized
Each type performs specific functions that maintain homeostasis
Tissues
Groups of cells similar in structure that perform common or related function
Histology
Study of tissues

TYPES OF PRIMARY TISSUES

Epithelial tissue
Covers
Connective tissue
Supports
Muscle tissue
Produces movement
Nerve tissue
Controls

EPITHELIAL TISSUE

Form boundaries
Two main types (by location)
Covering and lining epithelia
On external and internal surfaces
Glandular epithelia
Secretory tissue in glands

EPITHELIAL TISSUE FUNCTIONS

Protection
Absorption
Filtration
Excretion
Secretion
Sensory reception

5 CHARACTERISTICS OF EPITHELIAL TISSUE

Polarity
Specialized contacts
Supported by connective tissues
Avascular, but innervated
Can regenerate

POLARITY

Cells have polarity
Apical surface (upper free) exposed to exterior or cavity
Basal surface (lower, attached)
Both surfaces differ in structure and function

APICAL SURFACE OF EPITHELIAL TISSUE

May be smooth & slick
Most have microvilli (e.g., brush border of intestinal lining)
Increase surface area
Some have cilia (e.g., lining of trachea)

BASAL SURFACE OF EPITHELIAL TISSUE

Noncellular basal lamina
Glycoprotein and collagen fibers lies adjacent to basal surface
Adhesive sheet
Selective filter
Scaffolding for cell migration in wound repair

CHARACTERISTICS OF EPITHELIAL TISSUE:SPECIALIZED CONTACTS

Covering and lining epithelial tissues fit closely together
Form continuous sheets
Specialized contacts bind adjacent cells
Lateral contacts (See Fig 3.5)
Tight junctions
Desmosomes

CONNECTIVE TISSUE SUPPORT(EIPTHELIAL CHARACT.)

All are supported by connective tissue
Reticular lamina
Deep to basal lamina
Network of collagen fibers
Basement membrane
Basal lamina + reticular lamina
Reinforces epithelial sheet
Resists stretching and tearing
Defines epithelial boundary

AVALASCULAR BUT INVERTED(EPI. CHARACT)

No blood vessels in epithelial tissue
Must be nourished by diffusion from underlying connective tissues
Is supplied by nerve fibers

REGENERATION (EPI. CHARACT.)

High regenerative capacity
Stimulated by loss of apical-basal polarity and lateral contacts
Some exposed to friction
Some exposed to hostile substances
If adequate nutrients are present, can replace lost cells by cell division

CLASSIFICATION OF EPITHELIA

All epithelial tissues have two names
One indicates number of cell layers
Simple epithelia = single layer of cells
Stratified epithelia = two or more layers of cells
Shape can change in different layers
One indicates shape of cells
Squamous
Cuboidal
Columnar
In stratified epithelia, epithelia classified by cell shape in apical layer

CELL OF EPITHELIAL TISSUES

Squamous cells
Flattened and scalelike
Nucleus flattened (ovoid)
Cuboidal cells
Boxlike
Nucleus round
Columnar cells
Tall; column shaped
Nucleus elongated (ovoid)

SIMPLE EPITHELIA

Absorption
Secretion
Filtration
Very thin

SIMPLE SQUAMOUS EPITHELIUM

Cells flattened laterally
Cytoplasm sparse
Function where rapid diffusion is priority
i.e., kidney, lungs
Note description, function, location on next slide
Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia.
Function: Allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae.
Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae).

SIMPLE SQUAMOUS EIPTHELIUM 2 OTHER LOCATIONS

Two other locations
Endothelium
The lining of lymphatic vessels, blood vessels, and heart
Mesothelium
The epithelium of serous membranes in the ventral body cavity

SIMPLE CUBOIDAL EPITHELIUM

Single layer of cells
Secretion
Absorption
Forms walls of smallest ducts of glands and many kidney tubules
Description: Single layer of
cubelike cells with large, spherical central nuclei
Function: Secretion and absorption.
Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface.

SIMPLE COLUMNAR EPITHELIUM

Single layer of tall, closely packed cells
Absorption
Secretion
Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells).
Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action.
Location: Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.

PSEUDOSTRATIFIED COLUMNAR EPITHELIUM

Cells vary in height
Cell nuclei at different levels
Appears stratified, but is not
Secretion
Absorption
Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia.
Function: Secrete substances, particularly mucus; propulsion of mucus by ciliary action
Location: Nonciliated type in male's sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.

STRATIFIED EPI TISSUES

Two or more cell layers
Regenerate from below
Basal cells divide, cells migrate to surface
More durable than simple epithelia
Protection is major role

STRATIFIED SQUAMOUS EPITHELIUM

Most widespread of stratified epithelia
Free surface squamous; deeper layers cuboidal or columnar
Located for wear and tear
Those farthest from basal layer (and therefore nutrients) less viable
Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.
Function: Protects underlying tissues in areas subjected to abrasion.
Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane.

STRATIFIED CUBODIAL EPITHELIUM

Quite rare
Found in some sweat and mammary glands
Typically two cell layers thick

STRATIFIED COLUMNAR EPITHELIUM

Limited distribution in body
Small amounts in pharynx, male urethra, and lining some glandular ducts
Also occurs at transition areas between two other types of epithelia
Only apical layer columnar

TRANSITIONAL EPITHELIUM

Forms lining of hollow urinary organs
Basal layer cells are cuboidal or columnar
Ability to change shape with stretch
Apical cells vary in appearance
Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch.
Function: Stretches readily, permits stored urine to distend urinary organ.
Location: Lines the ureters, bladder, and part of the urethra.

GLADULAR EPITHELIA

Gland
One or more cells that makes and secretes an aqueous fluid called a secretion
Classified by
Site of product release—endocrine or exocrine
Relative number of cells forming the gland
unicellular (e.g., goblet cells) or multicellular

ENDOCRINE GLANDS

Ductless glands
Secretions not released into a duct
Secrete (by exocytosis) hormones that travel through lymph or blood to their specific target organs
Target organs respond in some characteristic way

EXOCRINE GLANDS

Secretions released onto body surfaces (skin) or into body cavities
More numerous than endocrine glands
Secrete products into ducts
Examples include mucous, sweat, oil, and salivary glands

MULTICELLULAR EXOCRINE GLANDS

Multicellular exocrine glands are composed of a duct and a secretory unit
Usually surrounded by supportive connective tissue
Supplies blood and nerve fibers
Extends into and divides gland into lobes

CLASSIFICATION OF MULTICELLULAR GLANDS

By structure and type of secretion
Structure
Simple glands (unbranched duct) or compound glands (branched duct)
Cells tubular, alveolar, or tubuloalveolal
Type of secretion
Merocrine - most - secrete products by exocytosis as produced
Holocrine - accumulate products within then rupture
Apocrine - accumulates products within but only apex ruptures - controversy if exist in humans

CONNECTIVE TISSUE

Most abundant and widely distributed of primary tissues
Four main classes
Connective tissue proper
Cartilage
Bone
Blood

MAJOR FUNCTIONS OF CONNECTIVE TISSUE

Binding and support
Protecting
Insulating
Storing reserve fuel
Transporting substances (blood)

CHARACT. OF CONNECTIVE TISSUE

Three characteristics make connective tissues different from other primary tissues
Have mesenchyme (an embryonic tissue) as their common tissue of origin
Have varying degrees of vascularity (blood vessels)
Have extracellular matrix
Connective tissue not composed mainly of cells
Largely nonliving extracellular matrix separates cells
So can bear weight, withstand tension, endure abuse

STRUCTURAL ELEMENTS OF CONNECTIVE TISSUE

Three elements
Ground substance
Fibers
Cells
Composition and arrangement varies in different connective tissues

GROUND SUBSTANCE

Unstructured material that fills space between cells
Medium through which solutes diffuse between blood capillaries and cells
Components
Interstitial fluid
Cell adhesion proteins ("glue" for attachment)
Proteoglycans
Protein core + large polysaccharides (chrondroitin sulfate and hyaluronic acid)
Trap water in varying amounts, affecting viscosity of ground substance

CONNECTIVE TISSUE FIBERS

Three types of fibers provide support
Collagen
Strongest and most abundant type
Tough; provides high tensile strength
Elastic fibers
Networks of long, thin, elastin fibers that allow for stretch and recoil
Reticular
Short, fine, highly branched collagenous fibers (different chemistry and form than collagen fibers)
Branch, forming networks that offer more "give"

CELLS

"Blasts" cells
Immature form; mitotically active; secrete ground substance and fibers
Fibroblasts in connective tissue proper
Chondroblasts in cartilage
Osteoblasts in bone
Hematopoietic stem cells in bone marrow
"Cyte" cells
Mature form; maintain matrix
Chondrocytes in cartilage
Osteocytes in bone

OTHER CELL TYPES IN CONNECTIVE TISSUE

Fat cells
Store nutrients
White blood cells
Neutrophils, eosinophils, lymphocytes
Tissue response to injury/ infection
Mast cells
Initiate local inflammatory response against foreign microorganisms they detect
Macrophages
Phagocytic cells that "eat" dead cells, microorganisms; function in immune system

TISSUE PROPER

All connective tissues except bone, cartilage and blood
Two subclasses
Loose connective tissues
Areolar
Adipose
Reticular
Dense connective tissues (also called fibrous connective tissues)
Dense regular
Dense irregular
Elastic

AREOLAR CONNECTIVE TISSUE

Support and bind other tissues
Universal packing material between other tissues
Most widely distributed
Provide reservoir of water and salts
Defend against infection
Store nutrients as fat
Fibroblasts
Loose arrangement of fibers
Ground substance
When inflamed, soaks up fluid  edema

CONNECTIVE TISSUE PROPER-CONNECTIVE TISSUE-AREOLAR

Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells.
Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid.
Location: Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries.

ADIPOSE TISSUE

White fat
Similar to areolar but greater nutrient storage
Cell is adipocyte
Stores nutrients
Scanty matrix
Richly vascularized
Shock absorption, insulation, energy storage
Brown fat
Use lipid fuels to heat bloodstream not to produce ATP
Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet.
Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs.
Location: Under skin in subcutaneous tissue; around kidneys and eyeballs; within abdomen; in breasts.

RETICULAR CONNECTIVE TISSUE

Resembles areolar but fibers are reticular fibers
Fibroblasts called reticular cells
Supports free blood cells in lymph nodes, the spleen, and bone marrow
Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network.
Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages.
Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).

DENSE REGULAR CONNECTIVE TISSUE

Closely packed bundles of collagen fibers running parallel to direction of pull
White structures with great resistance to pulling
Fibers slightly wavy so stretch a little
Fibroblasts manufacture fibers and ground substance
Few cells
Poorly vascularized
Description: Primarily parallel
collagen fibers; a few elastic fibers;
major cell type is the fibroblast.
Function: Attaches muscles to
bones or to muscles; attaches
bones to bones; withstands great
tensile stress when pulling force is
applied in one direction.
Location: Tendons, most
ligaments, aponeuroses.

DENSE IRREGULAR CONNECTIVE TISSUE

Same elements but bundles of collagen thicker and irregularly arranged
Resists tension from many directions
Dermis
Fibrous joint capsules
Fibrous coverings of some organs
Description: Primarily irregularly
arranged collagen fibers; some
elastic fibers; fibroblast is the
major cell type.
Function: Withstands tension
exerted in many directions;
provides structural strength.
Location: Fibrous capsules of
organs and of joints; dermis of the
skin; submucosa of digestive tract

CARTILAGE

Chondroblasts and chondrocytes
Tough yet flexible
Lacks nerve fibers
Up to 80% water - can rebound after compression
Avascular
Receives nutrients from membrane surrounding it
Perichondrium
Three types of cartilage:
Hyaline cartilage
Elastic cartilage
Fibrocartilage
Description: Amorphous but firm
matrix; collagen fibers form an
imperceptible network;
chondroblasts produce the matrix
and when mature (chondrocytes)
lie in lacunae.
Function: Supports and reinforces;
serves as resilient cushion; resists
compressive stress.
Location: Forms most of the
embryonic skeleton; covers the
ends of long bones in joint cavities;
forms costal cartilages of the ribs;
cartilages of the nose, trachea, and
larynx.

CARTILAGE ELASTIC

Description: Similar to hyaline
cartilage, but more elastic fibers
in matrix.
Function: Maintains the shape of
a structure while allowing great
flexibility.
Location: Supports the external
ear (pinna); epiglottis.

FIBROCARTILAGE

Description: Matrix similar to but
less firm than that in hyaline
cartilage; thick collagen fibers
predominate.
Function: Tensile strength allows
it to absorb compressive shock.
Location: Intervertebral discs;
pubic symphysis; discs of knee
joint.

BONE

Also called osseous tissue
Supports and protects body structures
Stores fat and synthesizes blood cells in cavities
More collagen than cartilage
Has inorganic calcium salts
Osteoblasts produce matrix
Osteocytes maintain the matrix
Osteons - structural units
Richly vascularized

BLOOD

Most atypical connective tissue - is a fluid
Red blood cells (RBCs) most common cell type
Also contains white blood cells (WBCs) and platelets
Fibers are soluble proteins that precipitate during blood clotting
Functions in transport

MUSCLE

Highly vascularized
Responsible for most types of movement
Three types
Skeletal muscle tissue
Found in skeletal muscle
Voluntary
Cardiac muscle tissue
Found in walls of heart
Involuntary
Smooth muscle tissue
Mainly in walls of hollow organs other than heart
Involuntary

NERVOUS TISSUE

Main component of nervous system
Brain, spinal cord, nerves
Regulates and controls body functions
Neurons
Specialized nerve cells that generate and conduct nerve impulses
Neuroglia
Supporting cells that support, insulate, and protect neurons

COVERING AND LINING MEMBRANES

Composed of at least two primary tissue types
An epithelium bound to underlying connective tissue proper
Are simple organs
Three types
Cutaneous membranes
Mucous membranes
Serous membranes

CUTANEOUS MEMBRANE

Skin
Keratinized stratified squamous epithelium (epidermis) attached to a thick layer of connective tissue (dermis)
Dry membrane

MUSCOUS MEMBRANES

Mucosa indicates location not cell composition
All called mucosae
Line body cavities open to the exterior (e.g., Digestive, respiratory, urogenital tracts)
Moist membranes bathed by secretions (or urine)
Epithelial sheet lies over layer of connective tissue called lamina propria
May secrete mucus

SEROUS MEMBRANES

Serosae—found in closed ventral body cavity
Simple squamous epithelium (mesothelium) resting on thin areolar connective tissue
Parietal serosae line internal body cavity walls
Visceral serosae cover internal organs
Serous fluid between layers
Moist membranes
Pleurae, pericardium, peritoneum

TISSUE REPAIR STEP 1

Necessary when barriers are penetrated
Cells must divide and migrate
Occurs in two major ways
Regeneration
Same kind of tissue replaces destroyed tissue
Original function restored
Fibrosis
Connective tissue replaces destroyed tissue
Original function lost

TISSUE REPAIR STEP 2

Organization restores blood supply
The blood clot is replaced with granulation tissue
Epithelium begins to regenerate
Fibroblasts produce collagen fibers to bridge the gap
Debris is phagocytized

TISSUE REPAIR STEP 3

Regeneration and fibrosis
The scab detaches
Fibrous tissue matures; epithelium thickens and begins to resemble adjacent tissue
Results in a fully regenerated epithelium with underlying scar tissue

REGENERATIVE CAPACITY IN DIFFERENT TISSUES

Regenerate extremely well
Epithelial tissues, bone, areolar connective tissue, dense irregular connective tissue, blood-forming tissue
Moderate regenerating capacity
Smooth muscle and dense regular connective tissue
Virtually no functional regenerative capacity
Cardiac muscle and nervous tissue of brain and spinal cord
New research shows cell division does occur
Efforts underway to coax them to regenerate better

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