72
UNIT 2
Basic Tissues
Figure 4-16A.
Loose connective tissue, mesentery.
Verhoeff
stain,
3
112; inset
3
200
Loose connective tissue
, also called
areolar connective tissue
, in
a mesentery spread preparation is shown. In this tissue prepara-
tion, both
collagen f bers
and
elastic f
bers
are visible. The elastic
F bers stain deep blue as thin strands and collagen F
bers appear as
thick, purple bundles.
Fibroblasts
are seen among the F bers. This
type of connective tissue has abundant ground substance, with
many connective tissue cells and relatively few F
bers. It is richly
vascularized, fl
exible, and not highly resistant to stress.
SYNOPSIS 4-2
Functions of Connective Tissue
Connective Tissue Proper
Dense irregular connective tissue
: Provides strong F
ber meshwork to resist stress from all directions (e.g., dermis of the
skin) and provides protective covering of organs (e.g., capsule of the kidney).
Dense regular connective tissue
: Provides resistance to traction forces in a single speciF c direction (e.g., tendons, ligaments).
Loose connective tissue
: Provides suspension and support for tissues that are not subjected to strong forces and forms
conduits in which vessels and nerves course. Cells in loose connective tissue have defense and immune functions (e.g.,
lamina propria of the digestive tract).
Specialized Connective Tissues
Adipose connective tissue
: Provides both cushioning for organs and energy storage; some involved in hormone secretion
such as leptin (e.g., hypodermis of the skin, mammary glands).
Reticular connective tissue
: Provides supportive framework for hematopoietic and solid (parenchymal) organs (e.g., liver,
pancreas).
Elastic connective tissue
: Provides distensible support and accommodates pressure changes on the walls of the arteries
closest to the heart (e.g., vertebral ligaments, large arteries).
Embryonic Connective Tissues
Mesenchymal connective tissue
: Gives rise to all types of connective tissues (embryonic mesoderm).
Mucous connective tissue
: Provides cushioning for the nucleus pulposus of the intervertebral disk and helps prevent
kinking in the blood vessels of the umbilical cord.
Collagen
Collagen
fiber
fiber
Elastic fibers
Elastic fibers
Elastic fiber
Elastic fiber
Collogen fiber
Collogen fiber
Fibroblast
Fibroblast
Collagen
fiber
Elastic fibers
Elastic fiber
Collagen fiber
Fibroblast
A
Loose connective tissue
Eosinophil
Fibroblast
Gut
epithelium
Plasma
cell
Macrophage
Plasma
cell
B
Figure 4-16B.
Loose connective tissue, large intestine:
H&E,
3
680; inset
3
1,506
The lamina propria of the digestive tract is an extreme example of
loose connective tissue
. This tissue lies immediately beneath the
thin
epithelium o± the gut
, which is one place where the body’s
defense mechanisms initially attack bacteria and pathogens.
Therefore,
plasma cells
, mast cells, leukocytes, and
f broblasts
are common in this area. Loose connective tissue is characterized
by loosely arranged, woven connective F
bers, abundant ground
substance, and tissue fl
uid, which contains the rich array of con-
nective tissue cells.
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