Ch. 4: Tissue Level of Organization

What are the 4 primary tissue classes?

Epithelial, connective, muscle, nervous

(multiple layers): Barrier for protection

Stratified epithelia

(single layer): Control transport/ absorption across membranes

Simple epithelia

Epithelial tissue

From left to right

Simple, pseudostratified, stratified

Shapes of epithelial tissue from left to right

squamous, cuboidal, columnar

Simple squamous epithelium

Muscle tissue

Skeletal muscle tissue

Nervous tissue

Nervous system

Connective tissue

Elastic connective tissue

form a tight seal between cells in a layer→ fluid/substances cannot leak between cells (epithelial cells)

Tight junction

hold cells together, fluid leaks around it (like snaps) (transitional epithelia)

Anchoring junction

channels connect cells together and allow ions and other solutes to pass between cells (cardiac myocytes)

Gap junction

Cells or organs that secrete substances for use elsewhere in the body (secretion) or release them for elimination from the body (excretion). Composed of epithelial tissue in a connective tissue framework

Glands

Gland that has no contact with the surface and has no ducts

Secrete (hormones) directly into blood

(ex) Thyroid, adrenal, and pituitary glands

Endocrine glands

Gland that maintains their contact with the body surface by way of a duct

(ex) Sweat glands, mammary glands, tear glands

Exocrine glands

Which organs have endo and exocrine functions?

liver, pancreas, gonads

Two structures of exocrine glands

Simple (single duct) and branched (multiple)

Two shapes of exocrine glands

Tubular & acinar (forms sac)

Exocrine gland modes of secretion:

Merocrine, apocrine, holocrine

Mode of secretion that has vesicles that release their secretion by exocytosis

• Cells remain intact

• Sweat glands, tear glands, pancreas, gastric glands

merocrine glands

Mode of secretion thicker, milkier secretion, containing fats

• Apical portion pinches off cell

• Sweat glands that develop with armpit and groin hair after puberty • In a few other places, including mammary glands

Apocrine glands

Mode of secretion where Cells accumulate a product, entire cell disintegrates

• Secretion is thick and oily→ cell fragments and synthesized substance

• Sebaceous glands of the skin and oil glands of scalp

• Oily secretion(sebum )coats hair shaft to protect it

holocrine glands

two ways tissues grow:

Increase # of cells (hyperplasia) or size of cells (hypertrophy)

Unspecialized tissues become specialized mature types

Differentiation

Changing from one type of mature tissue to another

Metaplasia

Uncontrolled tissue growth

• Composed of abnormal, nonfunctional tissue

- Tumor (benign or malignant)

Neoplasia

Damaged tissues can be repaired in two ways:

Regeneration & fibrosis

replacement of damaged cells by the same type of cells

• Restores normal function

• Skin injuries, liver generation

Regeneration

replacement of damaged cells with scar tissue

• Holds organs together

• Does not restore normal function

• Severe cuts and burns, healing of muscle injuries, scarring of lungs

Fibrosis

undifferentiated cells that are not yet performing any specialized function. Have potential to differentiate into one or more types of mature functional cell

Stem cells

a embryonic stem cell that can develop into any type of cell of the embryo plus the placenta and amniotic sac

totipotent

a embryonic stem cell that can develop into any type of cell of the embryo

pluripotent

an adult stem cell. bone marrow producing several blood cell types

multipotent

an adult stem cell where only one mature cell type produced (stem cells in epidermis)

unipotent