ANAPHY - 3M (Tissues)

Histology

the microscopic study of tissue structure

Tissues

groups of specialized cells and the extra-cellular substances surrounding them

• Epithelial Tissue

• Connective Tissue

• Muscle Tissue

• Nervous Tissue

Four Primary Tissue Types:

Epithelium

found both inside and outside of the body

Epithelium

it forms the layers that cover the surfaces and line the hollow organs of our body

Epithelium

especially important in hollow organs with openings to the outside environment

Epithelium

protects against foreign materials entering the body

• mostly composed of cells

• covers body surfaces

• nonvascular

Characteristics of Epithelial Tissue:

• protect underlying structures

• act as a barrier

• permit the passage of substances

• secrete and absorb substances

Major Function of Epithelial Tissue:

• Simple Epithelium

• Stratified Epithelium

• Pseudostratified Columnar Epithelium

Number of Layers or Category of Epithelia:

Simple Epithelium

• single layer of cells

• each cell extending from the basement membrane to the free surface

Stratified Epithelium

• more than one layer of cells

• only the deepest layer of cells attaches to the basement membrane

Pseudostratified Columnar Epithelium

• special type of simple epithelium

• one layer of cells, with all cells attached to the basement membrane

• appear to be two or more layers of cell, some cells are tall and extend to the surface, others are shorter and do not extend to the free surface

• Squamous

• Cuboidal

• Columnar

Shapes of Epithelial Cells:

Squamous

cells are flat or scalelike

Cuboidal

cells are cube-shaped, about as wide as they are tall

Columnar

(tall and thin, similar to a column) cells tend to be taller than they are wide

• Simple squamous epithelium

• Simple cuboidal epithelium

• Simple columnar epithelium

• Pseudostratified columnar epithelium

• Stratified squamous epithelium

• Transitional epithelium

Major Types of Epithelial Tissues:

Simple squamous epithelium

• single layer of thin, flat cells

• some substances easily pass through this thin layer of cells, others do not

• diffusion, filtration

Simple cuboidal epithelium

• single layer of cubelike cells

• carry out active transport, facilitated diffusion, secretion, absorption

Simple columnar epithelium

• single layer of tall, thin cells

• large size of these cells enables them to perform complex functions

Pseudostratified columnar epithelium

• single layer of cells, but cells appear to be layered due to the differing heights of adjacent cells and positions of their nuclei

• provides protection for the body

Stratified squamous epithelium

• consists of several layers of cells

• deepest cells are cuboidal or columnar

• capable of dividing and producing new cells

Transitional epithelium

• special type of stratified epithelium that can stretch

• (unstretched) five or more layers of cuboidal/columnar cells

• (stretched) cells flatten, number of cell layers decreases

Simple squamous epithelium

Location:

• body cavities (pleura, pericardial, peritoneal)

• endothelium of blood vessels

• lines lungs and capillaries

• kidney (bowman’s capsule)

Simple cuboidal epithelium

Location:

• walls of kidneys

• surfaces of ovaries

Simple columnar epithelium

Location:

• found in cilia

• gastrointestinal tract (digestive)

• fallopian tubes

Pseudostratified columnar epithelium

Location:

• Respiratory tract (nasal cavity, trachea, bronchii, pharynx)

Stratified squamous epithelium

Location:

• skin

• anus

• vagina

• mouth

• throat

• esophagus

• cornea

Transitional epithelium

Location:

• Urinary System (urinary bladder)

• Desmosomes

• Hemidesmosomes

• Tight Junctions

• Gap Junctions

Cell Connections:

Desmosomes

mechanically bind epithelial cells together

Hemidesmosomes

bind cells to the basement membrane

Tight Junctions

• form barriers

• anchor cells to each other

Gap Junctions

• allow for intercellular communication

• group of channels that allow small molecules and ions to pass from one epithelial cell to an adjacent one

Glands

• composed of epithelium supported by a network of connective tissue

• one or more cells responsible for secreting a particular product

• Endocrine Glands

• Exocrine Glands

Two Major Types of Glands:

Endocrine Glands

• produce chemicals called hormones

• ductless

Exocrine Glands

• secretions empty through ducts to the epithelial tissue

• with ducts

• Merocrine Gland

• Apocrine Gland

• Holocrine Gland

Three Types of Exocrine Glands

Merocrine Gland

sweat glands & exocrine pancreas

Apocrine Gland

eyelids, armpits and nipples

Holocrine Gland

sebaceous glands (oil glands)

• Enclosing and separating other tissues

• Connecting tissues to one another

• Supporting and moving parts of the body

• Storing compounds

• Cushioning and insulating

• Transporting

• Protecting

Functions of Connective Tissue:

• Protein Fibers

• Ground Substance

• Fluid

Three Major Components of Extracellular Matrix:

• Collagen fiber

• Reticular fiber

• Elastic fiber

Three Types of Protein Fibers:

Collagen fiber

• white

• very flexible but resist stretching

Reticular fiber

• very fine, short collagen fiber

• branch to form a supporting network

Elastic fiber

• yellow

• ability to return to their original shape after being stretched or compressed

Ground Substance

• gel-like mixture, consists of nonfibrous molecules

• mostly water along with adhesion proteins and polysaccharide molecules

• Loose Connective Tissue

• Dense Connective Tissue

Connective Tissue Proper:

Loose Connective Tissue

consists of relatively few protein fibers that form a lacy network, with numerous spaces filled with ground substance and fluid

• Areolar tissue

• Adipose tissue

• Reticular tissue

Three Subdivisions of Loose Connective Tissue:

Areolar tissue

Function:

• loose packing, support, and nourishment for the structures with which it is associated

Areolar tissue

Location:

• widely distributed throughout the body

• substance on which epithelial basement membranes rest

• packing between glands, muscle, and nerves

• attaches the skin to underlying tissues

Adipose tissue

Function:

• packing material, thermal insulator, energy storage

• protection or organs against injury from being bumped or jarred

Adipose tissue

Location:

• subcutaneous areas, mesenteries, renal pelvis, around kidneys

• attached to the surface of the colon, mammary glands

Reticular tissue

Function:

• provides a superstructure for lymphatic and hemopoietic tissues

Reticular tissue

Location:

• within the lymph nodes, spleen, bone marrow

Dense Connective Tissue

• relatively large number of protein fibers that form thick bundles and fill nearly all of the extracellular space

• Cartilage

• Bone

Supporting Connective Tissue:

Cartilage

composed of chondrocytes cells, located in spaces called lacunae within an extensive matrix

• Hyaline cartilage

• Fibrocartilage

• Elastic cartilage

Three Types of Cartilage:

Hyaline cartilage

• allows growth of long bones

• rigidity with some flexibility in the trachea, bronchi, ribs, and nose

• forms the embryonic skeleton

Fibrocartilage

• somewhat flexible and capable of withstanding considerable pressure

• connects structures subjected to a great pressure

Elastic cartilage

provides rigidity with even more flexibility than hyaline cartilage because elastic fibers return to their original shape after being stretched

Bone

a hard connective tissue that consists of living cells and a mineralized matrix

Muscle Tissue

to contract, or shorten, making movement possible

• Skeletal

• Cardiac

• Smooth

Three Types of Muscle Tissues:

Skeletal Muscle

Function:

• movement of the body

• voluntary control

Skeletal Muscle

Location:

attached to bone or other connective tissue

Cardiac Muscle

Function:

• pumps the blood

• involuntary control

Smooth Muscle

Function:

• regulates the size of organs, forces liquid through tubes, controls the amount of light entering the amount of light entering the eye

• produces “goose bumps” in the skin

• involuntary control

Smooth Muscle

Location:

In hollow organs, Stomach and Intestine skin and eyes

Nervous Tissue

• responsible for coordinating and controlling many body cavities

• composed of neurons and nerve support cells

• Neuron

• Glia

Nervous Tissue:

Tissue Membrane

thin sheet or layer of tissue that covers structure or lines a cavity

Mucous Membrane

open to the outside of the body

Serous Membrane

do not open to the exterior of the body

Synovial Membrane

line freely movable

Inflammation

defense mechanism that mobilizes the body’s immune cells to isolate and destroy microorganisms and other injurious agents

• Redness

• Heat

• Swelling

• Pain

• Disturbed function

5 Cardinal Signs:

Tissue Repair

substitution of viable cells for dead cells

• Regeneration

• Replacement

Tissue Repair:

Regeneration

new cells are the same type as those that were destroyed, and normal function is usually restored

Replacement

eventually produces a scar and causes loss of some tissue function

• Reduced rates of cell division and changes in the extracellular fibers.

• Collagen fibers become less flexible and have reduced strength.

• Elastic fibers become fragmented and less elastic

Effects of Aging in Tissues: