WEEK 2: Connective Tissue Flashcards
What is connective tissue?
An umbrella term that encompasses a wide variety of types including loose and dense, adipose, cartilage, bone and blood.
Function of connective tissue
- Support
- Protection
- Structure
- Store fat for energy
- Transports nutrients and waste (blood)
- Helps repair of damaged tissue.
Where is all connective tissue derived from?
Mesenchyme that produces:
- fibroblasts > fibrocyte
- chondrocytes > chondrocyte
- osteoblasts > osteocyte
- hematopoietic stem cells > blood cells
Continuation of layers:
- connective tissue proper > loose (areolar, adipose, reticular) and dense (regular, irregular, elastic)
- cartilage > hyaline, fibrocartilage, elastic
- osseous (bone) > compact, spongy
- blood
What are the three components of connective tissue?
- ground substance
- fibres
- cells
The ratio of these three components determines the type of tissue i.e., bone has heaps of ground substance, but blood vessels are super flexible.
What is the extracellular matrix?
- Non-cellular environment (ground substance and fibres)
- Provides a biomechanical environment for optimum cellular function.
Function of ground substance in connective tissue
- Gel substance in between fibres and cells
- Composed of water, proteoglycans, and cell adhesion proteins.
- Allows for the exchange of nutrients between cells and capillaries
Function of fibres in connective tissue
Provide strength and support.
3 TYPES:
COLLAGEN = large, strong fibres that provide tensile strength i.e., cartilage, ligaments, tendons (thick fibres)
ELASTIC = thin fibres that provide stretch and recoil i.e., aorta, lungs, and skin. (Wavy fibres)
RETICULAR = delicate fibres that crosslink to form a fine meshwork i.e., liver spleen and lymph nodes (branching, framework fibres)
Function of cells in connective tissue
- Functioning, living portion of tissue.
- Specialised cells tissue that are only found in some i.e., chondrocytes (cartilage), osteocytes (bone), and red blood cells.
- Common connective tissue cells found in more than one type i.e., fibroblast, mast cells, plasma cells, macrophages, adipocytes and leukocytes.
Cell types: fibroblast
- Most common cell
- Produce ground substance and fibres.
- Recognised by abundant rough ER. They need lots of protein to produce the substances.
- Large/ flat/spindle-shaped cells/ processes extend from the body.
- Immature fibrocytes are what produce the fibre and ground substances.
- Mature cells are concerned with the maintenance of the tissue and cellular metabolism.
Cell types: Mast cell
- Immune cells which mediate inflammation and allergic response
- Contain granules of chemical mediators (histamine, heparin, enzymes)
- When a cell comes into contact with an antigen/allergen, degranulation occurs, and the cell spits out the contents of the granule.
- Chemical mediators produce responses characteristic of an allergic reaction: increased permeability of blood vessels, and contraction of smooth muscles (airway).
Cell types: Macrophages
- Specialized phagocytosis
- Engulf and digest substances and cellular debris via phagocytosis.
- Identify the antigens on the substance, surround and engulf it, destroy it.
- Stimulate the action of other immune cells.
Cell types: Adipocyte
- Lipocytes or fat cells
- Store energy as fat, mainly in the form of triglycerides
- This can provide energy for long period of time.
- Typically, don’t make cells, but the cells hypertrophy (a fatter person holds more fat)
Cell type: Leukocyte
- Immune cells
- Defend body from infection and disease by digesting, destroying infectious agents or by antibodies
GRANULOCYTES (have granules in cytoplasm) – neutrophils, eosinophils and basophils.
AGRANULOCYTES (no granules) – monocytes and lymphocytes
What are the two common branches of connective tissue?
Proper = more common type (loose/dense)
Specialised = only found in one thing
What are the three branches of loose connective tissue?
LOOSE =
- lots of ground substance
- loose fibre arrangement (fewer fibres)
- found between tissues as a shock absorber
- can bind tissues together and allows water and nutrients to pass through due to ground substance.
3 TYPES: areolar, adipose and reticular
What is areolar connective tissue?
- Interlacing, loosely organised fibres with abundant blood vessels and ground substance.
- Attach epithelial tissue to underlying tissue i.e., skin, organs, and vessels.
What is adipose connective tissue?
- Loose collection of adipocytes, embedded in a mesh of collagen fibres.
- Store excess energy provides cushioning rand insulation i.e., bone marrow, surrounding organs, and underneath the skin.
What is reticular connective tissue?
- Branched mesh-like pattern of predominantly reticular fibres.
- Form a soft skeleton to support organs i.e., kidney, liver, spleen, lymph nodes.
What are the three branches of dense connective tissue?
DENSE = less ground substance, many fibres jammed in.
3 TYPES: regular, irregular, elastic
What is regular connective tissue?
- Predominately collagen fibres arranged in parallel bundles.
- Resists pulling forces from a single direction i.e. tendons, ligaments.
What is irregular connective tissue?
- Predominately collagen fibres but not arranged in parallel.
- Because they arranged this way, they can resist forces from different directions i.e., deep layers of the skin, sclera (white of eye), periosteum (outer layer of bone), submucosa of digestive tract.
What is elastic tissue?
- Composed of mostly elastic fibres.
- Ability to stretch and recoil i.e., layer within the walls of arteries and lungs.
What are the three types of specialised connective tissue?
3 TYPES: cartilage, bone, blood
What is hyaline cartilage?
HYALINE =
- Glass-like, translucent, avascular cartilage made up of primarily collagen fibres.
- Provides structure with limited flexibility i.e., nose, and trachea. Articular cartilage, embryonic skeleton.
What is fibrocartilage?
FIBROCARTILAGE =
- White-looking, densely arranged bundles of mostly collagen fibres.
- Resists weight bearing and compression forces i.e., interverbal discs, menisci, public symphysis.
What is elastic cartilage?
ELASTIC CARTILAGE =
- Chondrocytes within a network of elastic and college fibres.
- Provides strength and elasticity while maintain structure in non-weight bearing structures i.e., external ear, epiglottis, larynx.
What is bone connective tissue?
BONE =
- Osteocytes within hard extracellular matrix of calcium and phosphorus
What is blood connective tissue?
BLOOD = RBCs, WBCs and platelets
- Ground substance (plasma) and cells only (red, white and platelets).
