anatomy pt 2

Histology

The study of tissues; important to our understanding of the microscopic structures and functions

The Four Tissue Classes:

Epithelial

Connective

Muscle

Nervous

Epithelial

Closely spaced cells in layers that cover surfaces and organs; line cavities and ducts, form glands.

Connective

More extracellular material (matrix) than cell volume.

Muscle

Long excitable cells that generate force to move structures of the body.

Nervous:

Excitable cells that transmit pulses of information.

Function of Epithelia Tissues:

Physical protection

Permeability barriers

Innervations

Glandular secretion:

Structure of Epithelial Tissues

Located throughout the body forming the outer layer of skin; inner lining of body cavities, tubes, and ducts; covering over the viscera.

What is polarity in epithelial tissue?

Specific surfaces and uneven distribution of cell organelles.

What is the apical surface of epithelial tissue?

Exposed to the exterior of the body or into a body cavity or the interior (lumen) of an organ; may have cilia or microvilli.

What is the function of cilia in epithelial tissue?

Cilia beat synchronously and move substances.

What is the function of microvilli in epithelial tissue?

Microvilli expand the cell surface area, leading to more efficient absorption or secretion.

What is the lateral surface of epithelial tissue?

Faces the neighboring cells; connections to other cells.

What is the basal surface of epithelial tissue?

Adheres to the basement membrane or basal lamina.

What is the basal lamina in epithelial tissue?

Layer of glycoproteins and fibers that joins epithelial cells to connective tissue; border which helps make the free end of the cell easy to identify.

What is cellularity in epithelial tissue?

Cells are connected and fit tightly together with cell junctions.

How are epithelial cells attached?

Cells are attached to an underlying basal lamina.

What is avascularity in epithelial tissue?

Do not contain blood vessels; obtain nutrients by diffusion or active absorption.

How does epithelial tissue regenerate?

Tissues are able to replace damaged or lost cells, typically a very rapid process. Performed by stem cells within the epithelial tissue.

Tight junction:

Interlocking (zipper-like) adhesion belt fastens between cells that are impermeable

Gap junction

Plasma membrane channels join; ions, sugars and other small molecules can pass from

cell to cell; held together by connexons (membrane proteins), that form channels, essential

for coordinated muscle cell contractions in cardiac and smooth muscle.

Desmosone:

Dense areas, very strong and resist to mechanical stress (i.e. stretching and twisting);

abundant in the superficial layers of skin

Hemidesmosome

connects epithelial cells to the basal lamina.

What is simple squamous epithelium?

Thin, flat cells with flattened nucleus; rapid diffusion and secretion.

What is stratified squamous epithelium?

Multiple layers of cells that get flatter as they reach the surface; protection.

What is simple cuboidal epithelium?

Square cells with round nucleus; secretion and production of fluids.

What is stratified cuboidal epithelium?

Two or more layers of cuboidal cells; secretion.

What is simple columnar epithelium?

Tall, narrow cells with nucleus near bottom; absorption and secretion.

What is pseudostratified columnar epithelium?

All cells attached to basement membrane; secretion and propulsion of mucous.

What is transitional epithelium?

Tolerates stretching and recoiling; ranges from cuboidal to squamous.

Where is simple squamous epithelium found?

In air sacs of lungs, inner lining of heart and blood vessels, serous membranes of stomach and intestines.

What is the function of simple squamous epithelium?

Rapid diffusion or transport of substances; secretion of lubricating fluid.

Where is stratified squamous epithelium found?

In the skin, tongue, oral mucosa, esophagus, anal canal, and vagina.

What is the function of stratified squamous epithelium?

Protection from abrasion and penetration.

Where is simple cuboidal epithelium found?

In the liver, thyroid, mammary and salivary glands, kidney tubules.

What is the function of simple cuboidal epithelium?

Secretion and production of mucous, hormones, and fluids.

Where is stratified cuboidal epithelium found?

In the ducts of sweat glands and mammary glands.

What is the function of stratified cuboidal epithelium?

Secretion.

Where is simple columnar epithelium found?

In the intestines, uterus, and uterine tubes.

What is the function of simple columnar epithelium?

Absorption and secretion, movement of egg and zygote, secretion of mucous.

Where is pseudostratified columnar epithelium found?

In the respiratory tract from nasal cavity to bronchi, male reproductive tract.

What is the function of pseudostratified columnar epithelium?

Secretes and propels mucous.

What is the function of transitional epithelium?

Tolerates cycles of stretching and recoiling.

Endocrine Glands

ductless glands that secrete products (hormones) into the bloodstream or interstitial fluid (extracellular fluid). These secretions regulate metabolic and physiological activities; include pituitary gland, thyroid glands, and adrenal glands.

Exocrine Glands

connected by ducts to the skin surface or onto epithelium lining a passageway that opens to the outside (mouth). Different forms of secretion; include oil glands, sweat glands, mammary glands, and salivary glands.

What are merocrine glands?

Secretory product packaged by Golgi and released by exocytosis.

Give an example of merocrine glands.

Salivary glands.

What are apocrine glands?

Secretory product accumulates and pinches off from the apical surface of the cell.

What is an example of glands that are a combination of merocrine and apocrine?

Mammary glands.

What are holocrine glands?

Secretory product accumulates, cell bursts, and is replaced.

Give an example of holocrine glands.

Sebaceous glands (oil glands of the skin).

What are the types of secretions?

Serous, Mucous, Mixed exocrine

What is serous secretion?

Watery solution with enzymes; produced by parotid salivary glands

What is mucous secretion?

Mucins mixed with water to form mucous; produced by submucosal glands in the small intestine

What is mixed exocrine secretion?

Combination of serous and mucous; produced by submandibular salivary glands

What are the types of gland structures?

Unicellular Glands, Multicellular Glands

What are unicellular glands?

Single-celled glands found in goblet cells; secrete mucins in the small and large intestines, and trachea

What are multicellular glands?

Exocrine glands composed of many cells that form a distinctive structure

How are multicellular glands categorized?

By whether the ducts are branched or unbranched

What is a simple gland?

A gland with no branching ducts

What is a compound gland?

A gland with branching ducts

What are the secretory portions of glands?

Tubular (tubes), Acinar or alveolar (flask-like or bulb-like)

Properties of connective tissues

the most abundant tissue in the body, great variety of types and function

are not exposed to outside environment (unlike some epithelia)

consist of specialized cells, extracellular protein fibers and a ground substance, both

together constitute the matrix.

the ground substance contains water, proteins, glycoproteins, proteoglycans

clear, fluid, viscous (gelatinous), semisolid or solid, and colorless

cells (i.e. fibroblasts, melanocytes) are suspended in the matrix

Functions of connective tissue

establish a structural framework for the body

transport fluids and dissolved materials

protect organs

support, surround and interconnect other tissues

store energy reserves (lipids)

defend body from invading microorganisms

Connective tissue proper:

many types of cells and extracellular fibers in a syrupy ground substance.

Function: connection and protection

Loose (i.e. adipose tissue)

Dense (i.e. tendons)

Fluid connective tissue

specific groups of cells suspended in a watery matrix.

Function: transportation

Blood

Lymph

Supporting connective tissue

fewer types of cells suspended in a matrix densely packed with fibers.

Function: structural strength

Cartilage

Bone

What are the permanent resident cells of connective tissue?

Fibroblasts, adipocytes, and mesenchymal cells

What are the main functions of permanent resident cells in connective tissue?

Maintaining, repairing, and storing energy

What are the migratory cells in connective tissue?

Macrophages, mast cells, and lymphocytes

Where do migratory cells aggregate in connective tissue?

At sites of injuries

Fibroblasts

most abundant and always present, large star shaped cells that produce fibers (collagen, reticular and elastic) and proteoglycans for ground substance. Collagen: the most abundant protein in humans.

Macrophages

phagocytic cells that make up the first line of defense for the immune system; migrating around engulfing bacteria, foreign particles, dead/dying cells

two types: fixed macrophages (stay within tissue) and free macrophages (migrate

through tissues).

Adipocytes

adipose or fat cells; store lipids.

Mesenchymal cells

stem cells that form fibroblasts, macrophages, adipocytes, etc. (stem cell: unspecialized cell that divides into specialized daughter cells).

Melanocytes

synthesize and store the brown pigment melanin, color of tissue.

Mast cells

found near blood vessels; contain histamine (increases blood flow) and heparin (prevents blood clotting), which are released followed injury and lead to inflammation.

Lymphocytes

immune system cells, once developed into plasma cells they produce antibodies.

Collagen fibers

long, straight, and unbranched; most common; flexible yet stronger than steel when pulled from the ends, occurs in tendons, ligament, bones etc.

Reticular fibers

(reticulum = network) similar to collagen fibers in composition but form thin, branching networks; tough but flexible; cells, blood vessels, nerves are stabilized within the framework of reticular fibers.

Elastic fibers

contains the protein elastin, very thin, branched and wavy fibers, flexible and stretchable. Found between vertebrae.

Ground substance

Fills spaces between cells and surrounding connective tissue fibers. Because of

proteoglycans and glycoproteins is has a clear colorless and viscous appearance.

Thereby pathogens can move only slowly through it and phagocytes can catch up

and destroy them.

. Loose connective tissue

distributed throughout the body as a binding and packing material; irregular arrangement of fibers allows for flexibility and stretch in multiple directions. Found in organs, vessels, nerves etc.

Areolar tissue:

mostly ground substance, all 3 type of fibers including elastic fibers hence resilient to distortions. A loosely organized tissue, hence excellent for absorbs shock; contains many blood vessels (good place for injections). Found i.e. under the skin, muscle and skin can move independently.

Adipose tissue

adipocytes contain large droplet of lipid; other cell components (nucleus) are pushed to the side; (looks like a bunch of marshmallows), absorbs shocks, pads, insulates

White fat

Brown fat

adults; pale, yellow-white color

babies and young children; hibernating animals; highly vascularized, helps insulate and provide heat to blood (homeostasis)

Reticular tissue

fibrous supporting framework; spleen, liver, lymph nodes and bone marrow and lots of blood cells

Dense connective tissue

contains numerous, tightly packed fibers, mostly collagen; few blood vessels; slow to heal

Dense regular connective tissue

collagen fibers run parallel to each other and align with the forces applied to the area; contain many fibroblasts

tendons

ligaments

connect muscle to bone

bone to bone

Dense irregular connective tissue

web of fibers with no specific pattern; provides strength to resist forces applied from multiple directions; found under skin, forms protective sheath around cartilage and bone, forms a capsule over some organs (kidneys, liver, spleen) and encloses joints.

Elastic tissue

densely packed collagen fibers along with elastic fibers and fibroblasts; walls of large blood vessels, ligaments between vertebrae and penis.

Fluid connective tissue:

blood and lymph

Blood

plasma forms the watery ground substance that suspends the cells; contains red blood cells (erythrocytes), white blood cells (leukocytes & neutrophils, eosinophils, basophils, lymphocytes, monocytes), and platelets (fragments of cells important in clotting)

Lymph

- interstitial fluid that enters the lymphatic vessels; important in maintaining blood volume, role in immune system monitoring and essential for maintenance of homeostasis

What is perichondrium?

Protective sheath around cartilage

What are the types of cartilage?

Hyaline, elastic, and fibrocartilage

Where is hyaline cartilage found?

Connections between ribs and sternum, synovial joints, nasal cartilage, larynx, bronchi

What is elastic cartilage?

Mostly elastic fibers, extremely flexible

Where is elastic cartilage found?

Ear, epiglottis