Connective Tissue Flashcards
What is the function of connective tissue?
Bind, support and strengthen other body tissue
What is a specialised type of connective tissue?
Blood (major transport system)
Where is connective tissue found?
Bones, cartilage and blood (surface areas)
Connective tissue is highly vascular, with what exception?
Cartilage and tendons have a low blood supply
Connective tissue is composed of:
Extracellular matrix (ECM) and cells
What makes up the ECM?
Ground substance and protein fibres
What is ground substance made up of?
Water, proteins and polysaccharides (glycosaminoglycans)
What is the function of GAGS?
They join with core proteins to form proteoglycans, they are highly polar and attract water
What are proteoglycans?
A mix of proteins and sugars (glycosaminoglycans)
What do protein fibres do?
Provide structure, e.g bones are hard and inflexible, cartilage is firm and rubbery
What are monopolysaccharides?
Long chains of repeating sugar units
What are the 4 examples of sulphated GAGS?
Dermatan sulphate
Keratan sulphate
Heparin sulphate
Chondroitin sulphate
What is the function of sulphated GAGS?
They bind to proteins to form proteoglycans - complex molecules
What is the 1 non-sulphated GAG?
Hyaluronic acid
What are the functions of hyaluronic acid?
Traps water and makes the ground substance more jelly-like (so it is highly polar). It binds cells together, lubricates joints and maintains the shape of the eyeball
What is the enzyme hyaluronidase?
Makes the ground substance more liquid, creates easy access for cells (e.g easier access for sperm to get to egg)
Function of chondroitin sulphate:
Support/provide adhesive features of cartilage, bone, skin and blood vessels
Function of keratan sulphate:
Found in bone, cartilage and cornea, important for corneal development and maintenance
Function of dermatan sulphate:
Found in skin, tendons, bone, blood vessels, heart valves, it plays an important role in the structural integrity of the skin
Excessive ECM behind the eyes can lead to:
Overactive thyroid causing eyes to protrude, the response of the fibroblasts in the back of the eye
What are the features of collagen fibres?
Thick, strong, flexible, resist pulling forces
Where are collagen fibres found?
In bone, cartilage, tendons and ligaments (provides strength)
How do the features of collagen fibres vary?
Features vary in different tissue e.g more water around collagen in cartilage than in bone
What are the features of reticular fibres?
Composed of collagen and a coating of glycoprotein (mainly protein, few sugars). Thin, branching and spread through tissue
Reticular fibres are made by and they form:
Made from fibroblasts, form part of the basement membrane.
What do reticular fibres form?
Networks in vessels and tissue e.g adipose, nerve fibres, smooth muscle
Where are elastic fibres found?
Skin, blood vessels, lugs, things that can move and then return to their original position
What are elastic fibres made of?
The protein elastin surrounded by the glycoprotein fibrillin (for strength and stability)
Feature of elastic fibres:
Very thin
What causes Marfan’s syndrome?
Mutation in the gene on chromosome 15 coding for fibrillin
What is the function of the large glycoprotein, fibrillin?
Gives structural scaffold to elastin and produces a growth factor
What are fibroblasts?
Cells that are widely distributed in CT, they are migratory and can reconstruct the basement membrane
What is the function of fibroblasts?
They secrete components of the ECM e.g collagen
Where are adipocytes (fat cells) found and what are their functions?
Under the skin and around organs, they store fat (triglycerides)
What are macrophages? (also called histiocytes)
They are phagocytic cells (gobble up things like debris and bacteria) and are either fixed or wandering
What are plasma cells?
They come from B lymphocytes and produce antibodies
What are mast cells?
Cells that produce histamines that dilate blood vessels
What are leucocytes?
White blood cells that help fight infection/injury (found in the blood)
What is embryonic CT?
Gives rise to all other CT, consists of mesenchymal cells
What is mucous CT?
Widely scattered fibroblasts in jelly-like ground substance that supports the umbilical cord
What is areolar loose CT?
Contains all 3 fibres, provides strength, elasticity, support
What is adipose loose CT?
CT where fat cells dominate, two types: White adipose (energy storage) Brown adipose (heat production)
What makes loose CT different to dense CT?
Loose CT has fewer fibres and more cells, whereas dense CT has more fibres and fewer cells
Why does dense CT heal slower than loose CT?
Because it has fewer cells. Think of how tendons and ligaments take longer to heal.
What is dense regular CT?
Provides strength and connection. Found in areas where tensile strength is required (ligaments, tendons, aponeuroses)
Fibres are arranged in parallel bundles
What is dense irregular CT?
Fibres are NOT arranged in parallel bundles. MOstly consists of collagen fibres and is found in places where tearing by stretching forces may occur in different directions (found in the skin)
What is hyaline cartilage?
Provides movement and flexibility (weak) e.g nasal septum can move but stays in structure. Keeps nose, trachea open etc.
What is fibrocartilage?
Fibrocartilage is the tough, very strong tissue found predominantly in the intervertebral disks and at the insertions of ligaments and tendons.
What is elastic cartilage?
Elastic cartilage or yellow cartilage is a type of cartilage present in the outer ear. The principal protein is elastin.
Is cartilage vascular or avascular?
Cartilage does not contain blood vessels (it is avascular) Nutrition is supplied to the chondrocytes by diffusion. Compared to other connective tissues, cartilage has a very slow turnover of its extracellular matrix and does not repair.
What is compact bone?
The outer layer of bone. It forms long shafts known as cortical bone
What is spongy bone?
The porous inner bone tissue under the compact bone where bone marrow is found, also known as cancellous bone.
What does spongy bone produce, and what does it lack?
Produces red blood cells, lacks osteons
What are osteogenic cells?
Mesenchymal stem cells that lay down collagen. They become trapped in the collagen and become an osteoblast
What is an osteoblast?
Cells that lay down the matric and mineralises it to make the ECM rigid (lay down new bone)
What are osteocytes?
Mature bone cells derived from osteoblasts. They maintain bone tissue, have gap junctions and are involved in the exchange of nutrients/waste
What are osteoclasts?
Large multinucleated cells, formed by the fusion of blood monocytes (reabsorb dead bone (like in a shattered bone) and also remodel new bone
What are osteons?
They are a structural unit of compact bone that align along lines of stress e.g long axis of bone shaft
What does each osteon consist of?
Lamellae, lacunae, canaliculi and a central Haversian canal
What are the lamellae?
Rings of mineral sites for hardness (important for tensile strength. They form collagen and hydroxyapatite
What are the lacunae?
Small spaces between lamellae that contain mature bone cells (osteocytes)
What are the canaliculi?
‘Minute canals’ that have EC fluid that radiates from lacunae and provide routes for oxygen, waste and nutrients.
What is the central Haversian canal?
A canal that blood, lymph and nerves reside in
What does blood consist of?
Blood plasma (liquid ECM) and formed elements (red, white blood cells and platelets (platelets help with clotting)
What do chondroblasts do?
Lay down hyaline cartilage callus
