Connective Tissue Flashcards
(25 cards)
1
Q
Functions of Connective Tissue
A
- Provides an extracellular matrix that connects and
binds organs and cells within the body - Gives support to the body - forms fascia /tendons /cartilages /bones
- Facilitates cellular defence mechanisms
- Repair - forms scar tissue
- Provides an avenue for
communication/transportation - Connective tissue is (for the mostpart) directly supplied by blood and lymphatic vessels and nerves
2
Q
Fibroblast
A
- The principal cell of ordinary CT
- Produces the fibres (collagen and elastic fibres) and ground
substance - Abundant and irregularly branched cytoplasm with
extensive rER and well-developed Golgi apparatus - Quiescent fibroblasts are known as fibrocytes
3
Q
Collagen
A
- Type I: Provides tensile strength, 90% of total
collagen, dermis, ligaments, tendons, bone,
dentin - Type II: Found in hyaline and elastic cartilage
- Type III: Reticulin - first collagen secreted in
wound healing; lymphoid organs; affinity for
silver salts - Type IV: Found in the basal lamina
- Type VII: Forms anchoring fibrils e.g. anchors
basal lamina of epidermis to underlying dermal
fibre
4
Q
Elastic (fibre)
A
- Main component of elastic fibres is elastin
- Elastin gives tissues their elasticity (stretch &
recoil) - Found in dermis, elastic arteries (aorta), lung,
certain cartilages - Thin, branched fibres that require special stains
to be seen - Elastin core is covered with fibrils made up of the
glycoprotein fibrillin - Covalent bonds generate a cross-linked network
- Fibrillin is important in the assembly and integrity
of elastic fibres
5
Q
Reticular (fibre)
A
- Collagen type III
- Stain with silver salts
- Individual fibres – do not form bundles
- Provide a much more intimate form of
support - Found in high quantities in lymphatic
tissues/organs
6
Q
Disorders linked to collagen
A
Lack of Vitamin C can lead to
SCURVY
Vitamin C is essential for collagen
synthesis
Imperfect collagen production
causes abnormal bone growth,
fragile capillaries leading to
bleeding (gums), loss of teeth etc.
EHLER-DANLOS SYNDROME (EDS)
– a group of heritable disorders
Caused by a defect in the structure,
production, or processing of
collagen or proteins that interact
with collagen
Characterised by skin extensibility,
joint hypermobility and tissue
fragility.
7
Q
Disorder linked to elastin
A
Marfan Syndrome
* Defect in FBN1 gene which encodes fibrillin-1 i.e. lack
of fibrillin in elastic fibres
* Tall, thin individuals with long limbs, large hands,
sunken chest
* Defects of the heart valves and aorta - prone to aortic
rupture
* Typically have flexible joints and scoliosis
8
Q
Ground Substance
A
- Highly hydrated gel, interstitial (tissue) fluid
- Colourless and transparent; fills the space between the cells and fibres
- Functions:
- Resists compressive forces on the matrix – provides mechanical strength
- Molecular sieve through which nutrients, metabolites and hormones diffuse between blood
capillaries and cells - Composition:
- Composed primarily of glycosaminoglycans (GAGs), proteoglycans and adhesive glycoproteins
- Examples of GAGs include hyaluronic acid, keratan sulphate, chondroitin sulphate, heparin
sulphate
9
Q
Loose, Areolar (ordinary) CT
A
- Function: Holds structures in place
- “Packing” framework for organ support
- Pliable and mesh-like with widely
dispersed collagen and fibroblasts;
abundance of ground substance - Location:
- Widely distributed below epithelia
- Forms the lamina propria of a
mucosa - Surrounds capillaries
10
Q
Dense Irregular (ordinary) CT
A
- Predominant collagen fibres are densely packed and
irregularly arranged - Smaller proportion of ground substance compared to
loose CT - Function: Withstands tension in different directions
- Location:
- Dermis
- Submucosa of digestive tract
- Periosteum & perichondrium
- Fibrous capsules of organs
11
Q
Dense Regular (ordinary)
A
- Predominant collagen fibres run in parallel
- Function: maximum tensile strength
- Poor blood supply, therefore, when damaged, slow
to heal - Location:
- Ligaments (connect bone to bone)
- Tendons (connect muscle to bone)
- Aponeuroses (modified flattened tendons
found on the abdomen and back)
12
Q
Adipose (special) CT
A
- Composed of fat cells (adipocytes) that contain an individual lipid droplet,
surrounded by thin layer of cytoplasm & nucleus - Function:
- Energy store, cushions, insulation
- Metabolism of brown fat produces heat in the newborn
- Location:
- Under skin (e.g. hypodermis)
- Around kidneys
- Within abdomen
- Breasts
13
Q
Cartilage (special) CT
A
- Semi-rigid and strong but slightly flexible
- Withstands compression forces such as weight-bearing
but can also be bent (e.g. expansion of the rib cage) - It has a major role during development and growth of
long bones (endochondral ossification) - It is avascular - the cells in cartilage have to get their
oxygen and nutrients by long range diffusion
14
Q
Chondrocytes
A
- Develop from chondroblasts
- Produce the extracellular matrix
(fibres & ground substance) - Exist within matrix enclosed
compartments called lacunae - Young chondrocytes still able to divide produce little clusters or cell nests within the matrix
15
Q
Types of cartilage
A
Hyaline
* Articular surfaces of bones
* Trachea & Bronchus
* Costal cartilages
* Nasal cavity & nose
Elastic:
* Pinna of external ear
* Epiglottis
Fibrocartilage
* Tendon insertions
* Pubic symphysis
* Intervertebral discs
* Articular menisci
16
Q
Hyaline Cartilage
A
- Glassy or pearly white in appearance in the life situation
- Pale blue/purple (mottled) with H&E
- Matrix comprises collagen type II fibres embedded in a
firm hydrated gel of proteoglycans and structural
glycoproteins - High content of water bound to the GAGs acts as a shock
absorber – very important for articular cartilages
17
Q
Elastic Cartilage
A
- Very similar to hyaline
cartilage - Contains abundant
elastic fibres in
addition to collagen
type II - Flexible but also able
to spring back into
position
18
Q
Fibrocartilage
A
- Intermediate between dense
irregular CT and hyaline cartilage - Absence of perichondrium
- Chondrocytes usually arranged in
straight rows separated by
collagen type I fibres - Combines tensile strength with
shock absorption; resists
compression
19
Q
Osteoblasts
A
- Responsible for the production of the ECM
(collagen, proteoglycans, glycoproteins) - Development from an osteoprogenitor (stem)
cell - Presence of active osteoblasts required before
osteoid material can be deposited - Exclusively located at the surfaces of bone
tissue - Gradually surrounded by matrix and become
trapped in matrix – become osteocytes
20
Q
Osteocytes
A
- Principal bone cells of the adult skeleton
- Maintain the bone matrix
- Occur in small spaces in the mineralised matrix
– lacunae that are connected to each other via
small channels called canaliculi - Cytoplasmic processes of osteocytes extend
into the canaliculi - Canaliculi permit flow of nutrients and oxygen
through the matrix
21
Q
Osteoclasts
A
- Responsible for the resorption of bone
caused by releasing enzymes e.g.
collagenase and dissolving calcium salt
crystals - Derive from the monocyte phagocyte line
- Very large, motile cells
- Multinucleated with 5-50 nuclei
- Sit on bone surface often in depressions
called Howship’s Lacunae - Cell surface facing bone is highly folded –
forming a ruffled border
22
Q
Compact Bone
A
Also known as cortical
bone
Dense areas without
cavities
- Collagen fibres arranged in concentric lamellae around a canal (Haversian
canal) containing blood vessels and nerves – Osteon or Haversian System
23
Q
Spongy Bone
A
- Does not contain osteons
- Bone organised into plates of bone
called trabeculae/spicules - Lamellae within the trabeculae are
arranged concentrically – however
there is no central canal - Osteocytes sit in lacunae between
lamellae - Trabeculae sit adjacent to red
marrow spaces
24
Q
Periosteum
A
- Dense irregular CT covering outer surface of
bone - Contains osteoprogenitor cells
- Bundles of collagen fibres (Sharpey’s fibres)
penetrate the bone matrix – bind bone to
periosteum
25
Endosteum
* Single layer of osteoprogenitor cells and a very
small amount of CT
* Main function of both is to provide nutrients to
bone tissue and provision of new bone cells
