Lecture+outline+5+-+tissue+level+of+organization (2).docx -...

Biology 205-03: Human Anatomy and Physiology I
Fall 2017
Lecture outline 5: Tissue level of organization
Reading in Martini: Chapter 4
A. Introduction to tissues
1. General features of tissues
a. Aggregations of cells
1. All cells in a tissue may be similar in structure and function
2. In most tissues, several cell types are present – cells differ in structure and function
b. Every tissue includes cells and extracellular material
2. Four primary tissue types in humans (with subtypes of each primary tissue type)
a. Epithelial tissues: cover surfaces and line tubes
b. Connective tissues: protect, support, and bind other tissues
c. Muscle tissues are associated with movements
d. Nervous tissues: sense changes, communicate with other tissues, control and coordinate body
activities
B. Cell junctions
1. Plasma membrane specializations (protein complexes) at points of contact between neighboring cells
2. Types of junctions, with general functions of each
a. Adherens junctions anchor cells to neighboring cells
b. Desmosomes: focal junctions that anchor cells to neighboring cells
c. Hemidesmosomes: focal junctions that anchor cells to extracellular material
d. Tight junctions form fluid-tight seals between cells in a sheet
e. Gap junctions: communicating junctions that allow direct movement of ions and small molecules
from the cytosol of one cell to the cytosol of a coupled neighboring cell
C. Epithelial tissues
1. General features
a. Cells are tightly packed together, with little extracellular material
b. Junctions are prominent
c. Cells are arranged in sheets; an epithelial sheet may have a single layer of cells or more than one
layer of cells
d. Epithelial cells (and epithelial tissues) are polarized
1. Apical (free) and basal (attached) surface
2. Basal surface is anchored to a basement membrane (extracellular material)
e. Not penetrated by blood vessels (avascular) – must be near blood vessels in other tissues
f. Many epithelial tissues have a high capacity for renewal
1. Continual replacement of cells
2. High mitotic rate of stem cells associated with the epithelium
2. Functions of epithelia are related to location and structural details of the tissue…functions are not
necessarily mutually exclusive
a. Protection of underlying tissue
b. Filtration
c. Lubrication
d. Secretion
e. Digestion
f. Absorption