Chapter 4: Body Tissues and Membranes ~ 4.5 Extracellular Junctions, Glands and Membranes

Extracellular junctions

junctions between cells help cells function as tissue

Three types of extracellular juncitons

tight, gap and adhesion

Tight junction

plasma membrane proteins join, forming impermeable barrier

ex. zipper; allows urine to stay within kidney tubules

Gap junction

two adjacent plasma membrane channels join, alloweing substances to pass between tow cells

ex. cardiac cell synchronized contraction

Adhesion (demosome) junction

Adjacent plasma membranes held together by extracellular filaments

Ex. Cervix does not tip during childbirth

Glands

Consists of one or more cells that produce and secrete product; most composed primarily of epithelium

Two types of glands

Exocrine and endocrine

Exocrine

Secrete product into outer sugar or into a cavity

Ex. Goblet cells and sweat glands

Endocrine gland

Ductless and secrete their product internally to be transported by the bloodstream

Ex. Pituitary and thyroid glands