Unit 2 - Anatomical Organization, Histology, and Maintenance of Homeostasis

Cellular Organization

Cells → Tissue → Organ → Organ System → Organism

Tissues

A group of specialized cells which perform a specific function

4 Types of Tissues

• Epithelial, Connective, Muscular Nervous

Histology

The study of tissues

Epithelial Tissue

Characteristics:

• Upper (apical) surface of epithelium is free, or exposed to the outside of the body or to an internal body cavity. The lower (basal) surface rests on the connective tissue

• Basement membrane - forms between the epithelial and connective tissue

• Densely packed; little extracellular space between adjacent cells

• Avascular; lacks its own blood supply; nutrients diffuse from neighboring connective tissue

• Very high rate of mitosis; renwes/repairs itself rapidly

• UProtection, filtration, secretion, absorption, excretion

Upper (Apical) Surface

Surface exposed to the outside of the body or an internal body cavity

Lower (basal) surface

Surface that rests on connective tissue

Basement Membrane

Membrane that forms between the epithelial and connective tissue

Glandular Epithelium

Makes up secreting portions of exocrine and endocrine glands

Endocrine Glands

Secretions enter the extracellular fluid and diffuse into the bloodstream; no ducts; secretions are called hormones. Glands include adrenal, thyroid, and pituitary

Exocrine glands

Secrete products into a duct that leads to the surface of the skin or into the lumen (interior space) of a hollow organ. Glands include sweat and salivary glands. Hollow, lined by glandular epithelium

Merocrine

Cells secrete their substances by exocytosis. salivary and sudoriferous (sweat) glands

Apocrine

A portion of the cell membrane that contains the secretion buds off. Mammary and ceruminous (cerumen = earwax) glands

Holocrine

The entire cell disintegrates to excrete its substance. Sebaceous (oil) glands →sebum