153
CHAPTER FIVE
Tissues
Clinical Application 5.1 discusses the extracellular matrix
and its relationship to disease.
Connective tissue cells can usually divide. These tis-
sues have varying degrees of vascularity, but in most cases,
they have good blood supplies and are well nourished.
Some connective tissues, such as bone and cartilage, are
rigid. Loose connective tissue and dense connective tissue
are more fl
exible.
Major Cell Types
Connective tissues include a variety of cell types. Some of
them are called
f
xed cells
because they reside in the speciF c
connective tissue type for an extended period. These include
F broblasts and mast cells. Other cells, such as macrophages,
are
wandering cells.
They move through and appear in tissues
temporarily, usually in response to an injury or infection.
Fibroblasts
(F
bro-blastz) are the most common type of
F
xed cell in connective tissues. These large, star-shaped cells
produce F bers by secreting proteins into the extracellular
matrix of connective tissues
(f
g. 5.14)
.
bind structures, provide support and protection, serve as
frameworks, F ll spaces, store fat, produce blood cells, pro-
tect against infections, and help repair tissue damage.
Connective tissue cells are farther apart than epithelial
cells, and they have an abundance of
extracellular matrix
(eks
trah-sel
u-lar ma
triks) between them. This extracellu-
lar matrix is composed of
protein f
bers
and a
ground sub-
stance
consisting of nonF brous protein and other molecules,
and fl uid. The consistency of the extracellular matrix varies
from fl
uid to semisolid to solid. The ground substance binds,
supports, and provides a medium through which substances
may be transferred between the blood and cells of the tissue.
TABLE
5.4
|
Types of Glandular Secretions
Type
Description of Secretion
Example
Merocrine
glands
A f
uid product released
through the cell membrane
by exocytosis
Salivary glands, pancreatic
glands, sweat glands oF
the skin
Apocrine
glands
Cellular product and
portions oF the Free ends
oF glandular cells pinch o±
during secretion
Mammary glands,
ceruminous glands lining
the external ear canal
Holocrine
glands
Disintegrated entire
cells ²
lled with secretory
products
Sebaceous glands oF the
skin
TABLE
5.5
|
Epithelial Tissues
Type
Description
Function
Location
Simple squamous epithelium
Single layer, f
attened cells
³iltration, di±
usion, osmosis, covers
surFace
Air sacs oF lungs, walls oF capillaries, linings oF
blood and lymph vessels
Simple cuboidal epithelium
Single layer, cube-shaped cells
Secretion, absorption
SurFace oF ovaries, linings oF kidney tubules, and
linings oF ducts oF certain glands
Simple columnar epithelium
Single layer, elongated cells
Protection, secretion, absorption
Linings oF uterus, stomach, and intestines
Pseudostrati²
ed columnar
epithelium
Single layer, elongated cells
Protection, secretion, movement oF
mucus and substances
Linings oF respiratory passages
Strati²
ed squamous epithelium
Many layers, top cells f
attened
Protection
Outer layer oF skin, linings oF oral cavity, vagina,
and anal canal
Strati²
ed cuboidal epithelium
2 to 3 layers, cube-shaped cells
Protection
Linings oF larger ducts oF mammary glands,
sweat glands, salivary glands, and pancreas
Strati²
ed columnar epithelium
Top layer oF elongated cells,
lower layers oF cube-shaped cells
Protection, secretion
Part oF the male urethra and parts oF the
pharynx
Transitional epithelium
Many layers oF cube-shaped and
elongated cells
Distensibility, protection
Inner lining oF urinary bladder and linings oF
ureters and part oF urethra
Glandular epithelium
Unicellular or multicellular
Secretion
Salivary glands, sweat glands, endocrine glands
FIGURE 5.13
The sebaceous gland associated with a hair Follicle is a
simple-branched alveolar gland that secretes entire cells (40x).
Hair follicle
(hair shaft
removed)
Sebaceous
gland
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