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Connective Tissue – What is it?
Connective Tissue???
• It Binds, It Supports, It Strengthens, It Protects,
It Insulates, It Compartmentalizes, It helps us
move, It helps transport stuff, It is a site for
storing energy, It is involved in our immune
system, It helps heat us when we were itty bitty
babies!!!
• All Connective tissue is:
• Living cells within a non-living extracellular
matrix
- Extracellular Matrix (stuff between cells):
1. Protein Fibers
2. Ground substance
3-1
3-2
2. Connective Tissue
• Cells rarely touch due to extracellular matrix
• Matrix: Protein fibers & ground substance secreted by
cells
• Consistency varies from liquid, gel to solid
• Good nerve & blood supply (except cartilage & tendons)
• Most abundant, widely distributed, and histologically
variable of the primary tissues
Components of Connective Tissue
1. Cells
2. Non-living matrix
- Protein fibers
- Ground substance
1. Cells:
2.
blast type cells = 1) can divide & 2) secrete matrix
(fibroblasts, chondroblasts, & osteoblasts)
• cyte type cells = mature cells: reduced ability to divide or
produce matrix (chondrocytes & osteocytes)
5-4
3-3
Components Connective Tissue
Components of Fibrous Connective Tissue
more cells:
2. Non-living matrix
• leukocytes or white blood cells
- Types of Connective Tissue Fibers:
• Macrophages (develop from WBC)
– engulf bacteria & debris by phagocytosis
1.
• Plasma cells (develop from WBC)
– produce antibodies (proteins) that help attack foreign
substances
• Mast cells produce heparine & histamine
Collagen (25% of protein in your body)
- tough, resistant to pull, yet pliable
– tendons, ligaments, and deep layer of the skin are mostly
collagen
2. Elastic (protein elastin)
– can stretch and return to shape!
– very thin fibers
3. Reticular (spleen and lymph nodes)
– Support and strength
– thin collagen fibers coated with glycoprotein
• Adipocytes store fat
3-5
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Components of Fibrous Connective Tissue
2. Non-living matrix
- ground substance:
– usually gelatinous to
rubbery consistency
resulting from three classes
of large molecules
– glycosaminoglycans
(GAG)
– proteoglycan
– adhesive glycoproteins –
• Regulate H2O balance
• Slippery lubricant
• Adhesive
5-7
3-8
Types of connective tissue
1.
2.
3.
4.
5.
6.
7.
Loose Connective Tissues
•
Loose connective tissue (2)
Dense connective tissue (2)
Adipose tissue
Cartilage (3)
Bone (2)
Blood
Lymph?
Loosely woven fibers throughout tissues
2 Types of loose connective tissue
1. areolar connective tissue
2. reticular tissue
3-9
3-10
Areolar Tissue
Areolar Connective Tissue
Ground
substance
• Gelatinous ground
substance
• Few random protein
fibers (all 3 types)
• All 6 cell types
• Below our epithelial
layer !
(a)
Collagenous
fibers
Fibroblasts
(b)
Figure 5.14a
3-11
Elastic
fibers
Figure 5.14b,i
5-12
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Reticular Tissue
Reticular Connective Tissue
Reticular
fibers
Leukocytes
(a)
(b)
a: The McGraw-Hill Companies, Inc./Al Telser, photographer
Figure 5.15a
Figure 5.15b,i
• Network of fibers & cells that produce framework
to hold some organs together
5-14
3-13
1.
Dense Regular Connective Tissue
Dense Connective Tissue
•
More fibers present but fewer cells
•
Types of dense connective tissue:
1. dense regular connective tissue
2. dense irregular connective tissue
• Collagen fibers in parallel bundles with fibroblasts
3-16
3-15
2.
Dense Irregular Connective Tissue
Dense Irregular Connective Tissue
Bundles of
Gland
collagen fibers ducts
• Collagen fibers are irregularly arranged (interwoven)
• Tissues can resist tension from any direction
• Very tough tissue e.g., dermis of skin
3-17
(a)
Fibroblast Ground
nuclei
substance
(b)
a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer
Figure 5.17a
Figure 5.17b,i
5-18
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Adipose Tissue
Adipose Tissue
Blood
vessel
(a)
•
•
•
•
•
Adipocytes (store triglycerides)
Peripheral nuclei
Deeper layer of skin, organ padding, yellow marrow
Reduces heat loss, energy storage, protection
Brown fat??!!!
Adipocyte
nucleus
Lipid in
adipocyte
(b)
Figure 5.18a
Figure 5.18b,i
5-20
3-19
Hyaline Cartilage
Cartilage
•
•
•
Network of fibers in rubbery ground substance
Resilient and can endure more stress than loose
or dense connective tissue
Types of cartilage:
1. hyaline cartilage (invisible fibers)
2. fibrocartilage (thick collegen bundles)
3. elastic cartilage (visible elastic fibers)
• Chondrocytes!! sit in spaces called lacunae
• No blood vessels or nerves so repair is very slow
Articular cartilage
3-22
3-21
Elastic Cartilage
Hyaline Cartilage
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Matrix
(a)
Cell
nest Perichondrium
Lacunae
Chondrocytes
(b)
a: © Ed Reschke
Figure 5.19a
Figure 5.19b,i
• Elastic fibers help maintain shape after
deformations
• Ear, nose, vocal cartilages
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3-24
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Elastic Cartilage
Perichondrium
(a)
Elastic
fibers
Fibrocartilage
Lacunae
Chondrocytes
(b)
• Many more collagen fibers causes rigidity & stiffness
• Strongest cartilage (intervertebral discs)
• No perichondrium
a: © Ed Reschke
Figure 5.20a
Figure 5.20b,i
5-25
Fibrocartilage
3-26
Bone tissue (osseous tissue)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Collagen
fibers
(a)
•
Chondrocytes
Bones protect organs, allow for movement, store
minerals, sites of blood cell formation
• ‘bone’ has two meanings:
– an organ of the body; femur, mandible; composed
of multiple tissue types
– bone tissue – osseous tissue – makes up most of the
mass of bone
(b)
a: Dr. Alvin Telser
Figure 5.21a
Figure 5.21b,i
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2 types of bones: Compact and Spongy
1. Compact bone
– solid, dense bone
– basic unit of structure is osteon (haversian
system)
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Compact Bone
Blood
• Osteon = lamellae (rings) of mineralized matrix
– calcium & phosphate---give it its hardness
– interwoven collagen fibers provide strength
• Osteocytes surrounded by lacuna
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• Connective tissue with a liquid matrix = ??
• Cell types = red blood cells (erythrocytes), white blood
cells (leukocytes) and cell fragments (platelets)
• Transport things
• immune functions & clotting
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(1) Mucous Membranes
Membranes
•
•
•
Epithelial layer sitting on a thin layer of
connective tissue (lamina propria)
Combo of epithelial & underlying CT layer =
epithelial membrane
Types of membranes:
1. mucous membrane
2. serous membrane
3. synovial membrane
4. cutaneous membrane (skin)
• Lines cavity that open to the outside
– e.g., mouth, vagina, anus, respiratory
• Tight junctions between cells
• Mucous secreted by ?????
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3-31
(2) Serous Membranes
• Simple squamous cells overlying CT layer
• Squamous cells secrete slippery fluid
• Internal cavities (not open to the outside)
Examples:
– pleura, peritoneum and pericardium
– membrane on walls of cavity = parietal layer
– membrane over organs in cavity = visceral
layer
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(3) Cutaneous membrane (skin)
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(4) Synovial Membranes
Muscle
•
•
• Line joint cavities of freely movable joints
• No epithelial cells -- just special cells that secrete
slippery fluid
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Cells that shorten (myocytes)
Provide us with motion, posture and
heat
• Types of muscle:
1. skeletal muscle
2. cardiac muscle
3. smooth muscle
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Skeletal Muscle
Cardiac Muscle
• Cells are long cylinders with many peripheral
nuclei
• Visible banding (looks striated)
• Voluntary
• Cells are branched cylinders with one central
nuclei
• Involuntary
• striated
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Smooth Muscle
3-38
Tissue Growth
• Increasing the number of cells or the existing cells grow
larger
• hyperplasia - tissue growth through cell multiplication
• Spindle shaped cells with a single central nuclei
• Walls of hollow organs (blood vessels, GI tract,
bladder)
• Involuntary and nonstriated
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Sebaceous
gland cell
Fertilized
egg
Skin cell
Stem cell
Stem cell
Neuron
Astrocyte
Progenitor
cell
cells
Bone cells
Progenitor
cell
• neoplasia – development of a tumor (neoplasm)
– benign or malignant
– composed of abnormal, nonfunctional tissue
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Tissue Repair
Sperm
Egg
• hypertrophy - enlargement of preexisting cells
– muscle growth through exercise
– accumulation of body fat
• regeneration - replacement of dead or damaged cells by
the same type of cell as before
– restores normal function
– skin injuries and liver regenerate
• fibrosis - replacement of damaged cells with scar tissue
– holds organs together
– does not restore normal function
• severe cuts and burns, healing of muscle injuries,
scarring of lungs in tuberculosis
one or more steps
Fibroblasts (a connective tissue cells)
produces another stem cell
(self-renewal)
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Blood cells and platelets
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Wound Healing
Wound Healing
• severed blood vessels bleed
into cut
• mast cells and damaged
cells release histamine
– inhibits spread of pathogens
from injury site to healthy tissue
– dilates blood vessels
– increases blood flow to area
– makes capillaries more
permeable
• forms scab that temporarily
seals wound and blocks
infection
• blood plasma seeps into the
wound carrying:
• macrophages phagocytize
and digest tissue debris
1 Bleeding into the wound
– antibodies
– clotting proteins
– blood cells
– transform into soft mass –
granulation tissue
– macrophages remove the
blood clot
– begins 3-4 days after injury
and lasts up to 2 weeks
Scab
Blood clot
Macrophages
Fibroblasts
Leukocytes
2 Scab formation and
macrophage activity
Figure 5.33 (2)
5-43
Wound Healing
• deeper portions become
infiltrated by capillaries and
fibroblasts
• blood clot forms in the
tissue
5-44
Wound Healing
• surface epithelial cells
(mitosis)
Scab
• connective tissue
undergoes fibrosis
Macrophages
Fibroblasts
Blood
capillary
• remodeling (maturation)
phase begins several
weeks after injury and may
last up to two years
Granulation
tissue
3 Formation of granulation tissue
(fibroblastic phase of repair)
Figure 5.33 (3)
• scar tissue may or may not
show through epithelium
5-45
Epidermal
regrowth
Scar tissue
(fibrosis)
4 Epithelial regeneration and connective
tissue fibrosis (remodeling phase of repair)
Figure 5.33 (4)
5-46
Tissue Shrinkage and Death
• atrophy – shrinkage of a tissue through a loss in cell
size or number
– senile atrophy (aging)
– disuse atrophy (no use)
• necrosis – premature, pathological death of tissue (trauma,
toxins, or infections)
• apoptosis - programmed cell death
5-47
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