1. Histology Other topics

2. Extracellular Junctions Purpose: to allow cells to function as a unit (the definition of a tissue). They are connections along the lateral and basal sides of cells of a tissue. These connections allow cells to chemically “talk” to one another.

3. Extracellular Junction Types Tight Junctions: zipper-like connection between neighboring cells due to the membrane being bound together with the plasma membrane proteins. Impermeable. EX: Urine stays in kidney tubules because their cells are bound by tight junc. Gap Junctions: protein channels join together between neighboring cells. Helps in strength of tissue as well as allowing communication between the cells. EX: intercalated disks in cardiac muscle. Adhesion Junctions: (desmosomes and hemidesmosomes) plasma membranes don’t touch. Bound together with filaments attached in the cytoplasm.

4. Fig. 4.15a

5. Fig. 4.15b

6. Fig. 4.15c

7. Glands (Epithelium) Endocrine Glands: Ductless and associated with the production and release of hormones for the endocrine system. Exocrine Glands: Have a duct. Types: Apocrine: (Mammary and some sweat) discharge fragments of the epithelial cells with the secretion. Merocrine: (Sweat) release of contents without loss of cellular material. Holocrine: (Sebaceous/Oil) shed entire cells because the release of the substance kills the cell.

8. Fig. 4.16 Tubular, Alveolar, and Acini

9. Membranes Mucous: line tubes and organs that open to the outside. Composed of epithelium over connective tissue. Goblet cells secrete mucous. Serous: Synovial: line freely movable joint cavities and are composed of connective tissue. Meninges: Cutaneous: skin

10. Tissue Development In gastrulation (13-14 days after fertilization) three layers form in the ball of cells. Endoderm-forms into the inner gut Ectoderm-forms the skin and the nervous system Mesoderm-forms into bones, muscles, and blood vessels.