Lecture 6: Connective Tissue Flashcards
Three types of connective tissue
Embryonic
Adult
Special
Two types of embryonic ct
Mesenchyme
Mucous
4 types of adult connective tissue
Loose
Dense
reticular
adipose
Three types of special connective tissue
Cartilage
Bone
Blood
6 functions of connective tissue
- Connect
- Suspend/give form/subdivide
- Insulation and storage
- Defend
- Provide nutrition
- Repair and regeneration
5 Clinical relevancies of connective tissue
- Trauma/healing
- Inflammation
- Edema
- Vitamin C deficiency
- Tumor terminology/development
Two components of ct
Cells
Matrix
Two types of cells of Ct
resident
transient
Three components of the matrix of the ct
Fibers
Ground substance
Tissue fluid
Resident cells
- embryonic mesenchyme cells
- Always there
Examples of resident cells
Fibroblasts reticular cells adipocytes mesenchymal macrophages mast cells
Transient cells
- Hematopoietic stem cells
- Come and go
Examples of transient cells
plasma cells leukocytes neutrophils eosinophils basophils lymphocytes
Fibroblasts form
collagenous, elastic, and reticular fibers of the matrix
Macrophages
- Resident phagocytic cell of ct
- Can survive months in tissue
- May be named by located
Macrophages origin
From monocytes in blood. Once it enters ct, it is called a macrophage
Macrophages may be named by
location
ex. osteoclasts in bone
ex. kupffer cells in liver
Degranulation of mast cells causes
symptoms of allergy
Collagen fibers
white, very tensile and strong, do not stretch
Elastic fibers
Yellow, weak, and elastic, stretch and recoil
What are the most numerous fibers in the CT and bone?
Collagenous fibers
Collagen fiber structure
Extracellular scleroprotein fibers composed of fibrils usually arranges in bundles of indefinite length
Collagen fibers represent ____% dry weight in humans
30
4 Primary Types of Collagen Fibers
- Type 1: Resists tensile forces. Found in bone, dentin, tendons.
- Type 2: Resists compression. Forms fibrils found in cartilage
- Type 3: Reticular fibers found in stroma of expandable organs such as spleen, lymph node, liver, CV system, and lymphatics
- Type 4: basement membrane (basal membrane)
4 main types of collagen synthesis
Fibroblasts
Chondroblasts
Osteoblasts
Odontoblasts
Procollagen
Formed in the fibroblast, cleaved to tropocollagen outside the cell and then assembled into collagen fibrils
What is an important cofactor in collagen synthesis?
Vitamin C
3 Properties of collagen
- High tensile strength
- Poor shear strength
- Can only stretch 5% of initial length
Elastic fibers
Individual branching and anastomosing fibers; pink in H E but not easily detected, more evident with special stain
Yellow in natural color
Size of elastic fibers
0.2 - 5 um diameter in loose ct
Up to 12um in elastic ligaments
Can stretch up to 2.5 times original length
Where can elastic fibers be found (7)
Aorta artery Elastic artery Lungs Vocal chords Dermis Pinna of ear epiglottis
Reticulum
- A fine network formed by reticular fibers
- Can be stained by silver (argentaffin)
Collagen type 3 is synthesized by
Reticular cells, liver cells, smooth muscle cells, and skeletal muscle cells
The reticular ct serves as
a scaffolding for cells in lymph node, spleen, and bone marrow
Deficiency of collagen type III
Results in fragile skin syndromes
What is ground substance composed of?
Glycosaminoglycans (GAGS)
Proteoglycans
Glycoproteins
Properties of ground substance molecules allow for
- Binding of water
- Resisting compressive forces
- Cell adhesion to fibers
- Cell migration
- Barrier to bacterial/venom penetration
Common macromolecules of GAGs
- Hyaluronic acid
- Chondroitin sulfate
- Keratin sulfate
- Dermatan sulfate
- Heparan sulfate
4 types of structural glycoproteins
- Fibronectin
- Laminin
- Osteonectin (In bone)
- Chondronectin (In cartilage)
Proteoglycans
- Formed by covalently linking GAGs to protein core
- May regulate passage of molecules and cells in the intercellular space and in chemical signaling between cells
- Stain with basic dyes if present in high concentrations (hyaline cartilage )
Structural glycoproteins
Proteins with attached carbs, help attach cells to each other and to extracellular matrix
Proteoglycans: GAGs:
Where is hyaluronic acid found?
Vitreous humor of the eye, synovial fluid, umbilical cord, loose ct, skin, and cartilage
Proteoglycans: GAGs:
Where is chondroitin sulfate found?
cartilage, arteries, skin, and cornea
Proteoglycans: GAGs:
Where is keratin sulfate found?
cornea, cartilage, bone
Proteoglycans: GAGs:
Where is dermatan sulfate found?
Skin, tendons, sclera, and lungs
Proteoglycans: GAGs:
Where is heparin sulfate found?
arteries and lung
Connective tissue fluid
- Solution of nutrients and dissolved gases derived from plasma
- Bathes matrix and cells with nutrients, aids in removing waste
- Fluid dynamics maintain proper balance
- Lymphatics important in fluid movement and prevention of edema
Edema
Abnormal accumulation of tissue fluid
Mesenchyme
- Originates from the mesoderm and gives rise to adult ct
- Gel-like due to presence of ground substance, few fibers and star-shaped mesenchymal cells
Loose connective tissue
- Ubiquitous
- Loosely arranged fibers
- Cellular constituents vary with location
Dense connective tissue
Irregular and regularly arranged
Densely packed fibers
Strong tissue
Dense connective tissue
- Inactivated fibroblast = fibrocyte nuclei
- Parallel arranged collagenous fibers
- Very strong, resists tensile forces
- Found in tendons, ligaments, cornea
Adipose connective tissue is formed by
Adipocytes: cells with basement membrane
Functions of adipocytes (2)
- Energy storage
- Endocrine: adipocytes produce leptin which has a regulatory effect on body fat. Leptin levels are proportional to body fat. It signals to the brain (satiety center) that the body has had enough to eat
What makes something adipose tissue?
Adipocytes outnumber other cell types
Unilocular
White fat
Multilocular
Brown fat
Purpose of white fat
energy storage
insulation
Endocrine: leptin
Purpose of brown fat
heat generation
Brown adipose cells have many
mitochondria
Lipomas
Very common benign tumors generated by unilocular adipocytes
