Fundamentals of Anatomy and Physiology

Tissues 107

As the body Ages

Cells divide more rapidly in the young and much more slowly in older adults.
Therefore, injuries in older adults heal much slower and, occasionally, incom-
pletely, especially in regard to bone tissue. We notice a decrease in the athletic
abilities of individuals in their late 30s to early 40s. Muscle cells and functional
neurons decrease with age. Memory and brain capacity decline significantly with
the elderly.^
As we age, the tough collagen fibers become structurally irregular, resulting- in ligaments and
tendons being more fragile and less flexible. Elastic fibers become less elastic. We see gradual
increases over time in the wrinkling of the skin due^
to these connective tissue fiber changes. Thus, the older we get, the more we tend to use
moisturizing and fiber-containing cosmetic creams and lotions.

Career

Focus

These are careers that are available to individuals interested in the study of tissues. They

require training in microscopy to examine cellular structures.

●● Histologists are medical professionals specializing in the study of the structure and

function of tissues. They are employed in universities and medical centers.^

●● Forensic scientists specialize in analyzing tissue samples, looking for clues that help

solve crimes. They are employed by law enforcement agencies.

Summary Outline

Introduction

1.^ Histology is the study of tissues.^
2. The four kinds of tissue are epithelial, connective,
muscle, and nervous.

Epithelial Tissue

1. Epithelial tissue functions in four ways: it protects
   underlying tissues; it absorbs nutrients; it secretes
   hormones, mucus, and enzymes; and it excretes

waste like urea in sweat.^

2. The basement membrane acts as an anchor and ad-

hesive for epithelial cells.^

3. Epithelial tissue can be named according to shape,

arrangement, or function.^

4. Epithelial tissue is made of cells closely packed to-
   gether with very little intercellular material.

Classification Based on Shape

1. Squamous epithelial cells are flat and serve a
   protective- function like the lining of our mouths
   and our skin.^


2. Cuboidal epithelial cells are shaped like cubes and
   function in protection and secretion.^


3. Columnar epithelial cells are tall and rectangular.
   They function in secretion and absorption.

Classification Based on Arrangement

1.^ Simple epithelium is one cell layer thick.^
2.^ Stratified epithelium is several layers of cells thick.^
3. Pseudostratified epithelium looks like it is several
layers thick, but, in reality, all cells extend from the
basement membrane to the outer surface.^
4. Transitional epithelium consists of several layers-
of closely packed, easily stretched cells. When^
stretched they appear flat; when relaxed they look
ragged or saw-toothed.