Connective Tissue
Connective Tissue
Found everywhere in the body; most abundant type of tissue
Collagen is a major protein found in connective tissue
Also the most common protein found in the body
Functions:
Provides protection
Binds body tissues together
Supports the body
Connective Tissue Characteristics
Variations in blood supply
Some tissue types are well vascularized
Some have a poor blood supply or are avascular
Tendons, ligaments
Extracellular matrix (a unique feature)
Nonliving material that surrounds living cells
Secreted by the connective tissue cells
Extracellular Matrix
Two main elements comprise
the matrix:
Ground Substance
Fibers
Extra-cellular matrix:
Ground Substance
Secreted by the cells
Composed mostly of water
adhesion proteins and polysaccharide molecules (trap the water to
make a gel-like substance)
Extra-cellular matrix: Fibers
Secreted by the cells
Three types:
Collagen (white) fibers
Allow CT to withstand pulling/tension
Elastic (yellow) fibers
Contain elastin- allows stretching
Reticular fibers (a type of collagen)
Short fibers that create a network
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Connective Tissue Types
From most rigid to softest, (or most fluid):
Bone
Cartilage
Dense connective tissue
Loose connective tissue
Blood
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Connective Tissue Types
Bone (osseous tissue)
Composed of:
Osteocytes (bone cells) sitting in lacunae (cavities)
Hard matrix of calcium salts
Functions to protect and support the body
Figure 3.19a Connective tissues and their common body locations.
Bone
cells
in lacunae
Central
canal
Lacunae
Lamella
(a) Diagram:
Bone
Photomicrograph: Cross-sectional
view of ground bone (165×)
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Connective Tissue Types
Cartilage
more flexible than bone
Found in only a few places in the body
Chondrocyte (cartilage cell) is the major cell type
Three types of cartilage:
Hyaline
Elastic
Fibrocartilage
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Connective Tissue Types
Hyaline cartilage
Hyaline cartilage is the most widespread type of cartilage
Locations:
Larynx
Entire fetal skeleton prior to birth
Epiphyseal plates (ends of long bones)
Functions as a more flexible skeletal element than bone
Figure 3.19b Connective tissues and their common body locations.
Chondrocyte
(cartilage cell)
Chondrocyte
in lacuna
Matrix
Lacunae
Photomicrograph: Hyaline
cartilage
from the trachea (400×)
(b) Diagram:
Hyaline
cartilage
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Connective Tissue Types
Elastic cartilage
Provides elasticity
Location:
Supports the external ear
Fibrocartilage
Highly compressible
Location:
Vertebral discs of the spinal column for cushion
Figure 3.19c Connective tissues and their common body locations.
Chondro-
cytes in
lacunae
Collagen
fibers
Chondrocytes
in lacunae
Collagen fiber
Photomicrograph: Fibrocartilage of
an
intervertebral disc (150×)
(c) Diagram:
Fibrocartilage
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Connective Tissue Types
Dense connective tissue (dense fibrous tissue)
Main matrix element is collagen fiber made by fibroblasts
Locations:
Tendons—attach skeletal muscle to bone
Ligaments—attach bone to bone at joints and are more elastic than tendons
Dermis—lower layers of the skin
Figure 3.19d Connective tissues and their common body locations.
Ligament
(d) Diagram: Dense
fibrous
Photomicrograph: Dense fibrous
connective tissue from a tendon (475×)
Collage
n
fibers
Nuclei of
fibroblasts
Nuclei of
fibroblasts
Collagen
fibers
Tendo
n
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Connective Tissue Types
Loose connective tissue types
Areolar tissue
Most widely distributed connective tissue
Soft, pliable tissue like “cobwebs”
Functions as a universal packing tissue and “glue” to hold organs in place
Layer of areolar tissue called lamina propria underlies all membranes
Can soak up excess fluid (known as “edema”)
Figure 3.19e Connective tissues and their common body locations.
Mucosa
epithelium
Lamina
propria
Fibers of
matrix
Nuclei of
fibroblasts
Elastic
fibers
Collagen
fibers
Fibroblast
nuclei
(e) Diagram: Areolar
Photomicrograph: Areolar connective tissue,
a soft packaging tissue of the body (270×)
Connective Tissue Types
Loose connective tissue types
Adipose (fat) tissue
Many cells contain large lipid deposits with nucleus to one side (also called
“signet ring cells”)
Functions
Insulates the body
Protects some organs
Serves as a site of fuel storage
Figure 3.19f Connective tissues and their common body locations.
Nuclei of
fat cells
Vacuole
containing
fat droplet
Vacuole
containing
fat droplet
Nuclei
of
fat cells
(f) Diagram:
Adipose
Photomicrograph: Adipose tissue from
the
subcutaneous layer beneath the skin (570×)
Connective Tissue Types
Loose connective tissue types
Reticular connective tissue
Delicate network of interwoven fibers with reticular cells (like fibroblasts)
Locations:
Forms internal framework of certain organs, as:
Lymph nodes
Spleen
Bone marrow
Figure 3.19g Connective tissues and their common body locations.
Splee
n
(g) Diagram:
Reticular
Photomicrograph: Dark-staining
network
of reticular connective tissue (400×)
Reticular
cell
Blood
cell
Reticular
fibers
White blood cell
(lymphocyte)
Reticular fibers
Connective Tissue Types
Blood (vascular tissue)
Blood cells surrounded by fluid matrix known as blood plasma
Soluble fibers are visible only during clotting
Functions as the transport vehicle for the cardiovascular system,
carrying:
Nutrients
Wastes
Respiratory gases (oxygen and carbon dioxide)