Connective tissue Flashcards
Connective tissue definition
Responsible for connection and binding of cells and organs
Structural function of CT
- Form capsules that surround the organs and the internal architecture that support parenchymal cells
- Dense CT makes up tendons and ligaments
- Areloar CT fills up space between organs
- Bone and cartilage support soft tissue
Defensive function of CT
- CT provides a physical barrier preventing disperssion of micro-organisms that pass through the epithelia
- CT contains phagocytic cells that phagocytose organisms and produce substances that modulate infammation
- CT contains plasma cells that produce antibodies
Other functions of CT
Nuitritive function
Storage of fat
Embryonic origin of CT
Most CT is developed from the mesenchyme which develops from the mesoderm
Mesenchyme cells characteristics
They are rapidly dividing cells with high rate of protein synthesis
Nucleus: Oval with prominent nucleoli and fine chromatin
Cytoplasm: -Small in amount, have multiple thin processes
-Free ribosomes and mitochondria
Composition of CT
Extracellular matrix (ECM)
Cells
Blood vessels
Nerves
Extracellular matrix components
Ground amorphus substance
Fibres - Collagen
- Reticular
-Elastic
Ground amorphus substance description
Amorphous, colorless, transparent and homogenous substance
Contains water, minerals and polysaccharides like:
-Glycosaminoglycans (GAGs)
-Proteoglycans
-Glycoproteins
Glycosaminoglycans (GAGs)
Structure and types
Linear polysaccharides formed by repeated disaccharide units
The repeated disaccharide units are uronic acids and amino suragrs as hexosamines
TYPES:
-Non-sulphated GAGs: hyaluronic acid (long chain)
-Sulphated GAGs: chondrotin sulfate, dermatan sulfate, heparan sulfate, keratan sulfate (short chain)
Proteoglycans
structure and types
When sulfated GAGs are conjucated with an axial protein they are called proteoglycans
When several proteoglycans are bound to hyaluronic acid, they form proteoglycan-hyalurinate complex (in cartialge, basophilic)
Glycoproteins
Structure and types
Multi-adhesive macromolecules formed mainly of protein conjucated with few sugars or branched oligosaccharides Types: Fibronectin: present in CT Chondronectin: present in cartilage Laminin: Present in basal lamina
Glycoproteins compared with proteoglycans
In glycoproteins:
The protein moiety predominates
Do not contain linear polysaccharides
The carbohydrates are branched
Functions of GAGs
Supportive as in cartilage
Protection against bacteria
Bind growth factors and can inhibit and activate these factors
Transport tissue fluid through their meshes
Lubricant as in joints
Glycoproteins functions
Are multi-adhesive
Clinical correlation of the ground amorphous substance
Form a barrier against penetration
Hyaluriondase of certain bacteria can dissolve it though
Collagen functions
It is a strong, resistant, supportive element in ECM
Collagen structure
Collagen fibres is composed of fibrils
Collagen fibirils is composed of microfibrils
Microfibrils is composed of tropocollagen helices
Each triple helix is composed of 3 polypeptide chains
Collagen type I
Function, stie
- It is a basic protein that resists tension
- Present it: -CT proper -Fibrocartilage
Collagen type I
Medical applications
- Defective formation of collagen type I will cause spontaneous fractures and cardiac insufficiency leading to heart failure ( inherited genitic disease) this is called Osteogenesis imperfecta
- Keloid: Disfiguring local swelling caused by abnormal amounts of collagen in skin scars
- Scurvy: Lack of vitamin C (essential for hydroxylation of proline) causes ulceration of gums and hemorrhages
Collagen type II
Function, site
Resists pressure
Found in hyaline and elastic cartilage
Collagen type III
Function, site
Supportive in expansible organs
Present in :
-Loose and reticular CT
-Blood vessels
Collagen type III
Medical applications
Defective formation of colagen type III in the wall of aorta may lead to its ruptue (aneurysm)
Collagen type IV
Function, stie
Acts as a filter
Present in basal lamina
Collagen type V
Function, stie
Is present in asscociation with collagen type I
Present in:
-Fetal membranes
-Basement membranes
Collagen type VII
Function, stie
Anchoring/Linking collagen
Present in basment membranes
Cells seceting collagen fibres
- Fibroblasts
- Chondroblasts
- Odontoblasts
- Osteoblasts
- Vascular smooth muscle cells
Cells secreting elastic fibres
- vascular smooth muscle cells
- Chondroblasts
- Fibroblasts
Cells secreting reticular fibres
- Fibroblasts
- Schwann’s cells (Endoneurium)
- Vascular smooth muscle cells
- Hepatocytes (liver)
- Reticular cells in the spleen, lymph nodes and bone marrow
Staining of collagen fibres
Wish acidic dyes (Eosin) and Sirius red
Staining of reticular fibres
They have high content of sugar so they are PAS+ve (brown) and argyrophilic (with silver)
Staining of elastic fibres
Brown with orcein
Reticular fibres structure
Composed mainly of collagen type III in association with other types of collagen
Elastic fibres structure
Composed of
- Elastin protein
- Fibrillin (which is microfibril that forms a scaffold upon which elastin is deposited and present around and inside elastic fibres)
Clinical applications of elastic fibres
Marfan syndrome:
A defective genetic formation of fibrillin leads to lack of resistance in tissue rich in elastic fibres like aorta which becomes swollen forming an aneurysm and may rupture
Types of CT cells
Fixed cells
Transient cells
Fixed cells
Origin and example
The originate locally from undefferentiated mesenchymal cells and spend their life in the CT
Example:
-Fibroblasts
-Adipose cells
-Undefferentiated mesenchymal cells (UMC)
Transient cells
Origin and example
They come from hematopoietic stem cells in the bone marrow and travel to the CT by blood Examples: -Plsma cells -Mast cells -Macrophages -Leucocytes
Fibroblasts types
Active form :Fibroblast
Inactive form: Fibrocyte
Myofibroblast
Fibroblast
Shape and function
Irregular branched cells with cytoplasmic processes
Synthesis of collagen, reticular and elastic fibres
Synthesis of glycosaminoglycans and glycoproteins of the matrix
Fibroblasts
LM
Large ovoid nucleus, pale stained with fine chromatin and a prominent nucleolus
Abundant basophilia in the cytoplasm
Fibroblast
EM
Rich in rER
Well developed Golgi apparatus
Fibrocyte
size, LM, EM
SMaller than fibroblast Spindle shapped wth fewer proceses Smaller, elongated and darker nucleus Nearly acidophilic cytoplasm Few rER
Myofibroblast
Characteristics and function
Contains increased amount of actin and myosin microfilaments
Responsible for wound closure
Cells involved in the healing of wound and formation of scar:
- Fibroblasts
- Myofibroblasts
- Pericytes
The mononuclear phagocyte system
Macrophages distributed throughtout the body
Macrophage name in liver
Kupffer cells
Macrophage name in CNS
Microglial cells
Macrophage name in bone tissue
Osteoclasts
Macrophage name in Skin
Langerhan’s cells
Macrophage name in Lymph node
Dendritic cells
Macrophage name in Lungs
Dust cells
Macrophage name in blood
Monocytes
Macrophage name in connective tissue
Macrophages/Histocytes
All cells of the mononuclear phagocyte system have the same:
Morphology
Cell surface receptors
Enzymes of lysozome
Are capable of phagocytosis
Mononuclear phagocyte system stains
By injection of vital dyes (Trypan blue or Indian ink)
Macrophages
LM shape, cytoplasm and nucleus
Irregular surface with protrusions and indentations
Basophilic cytoplasm that contains many small vacuoles and dense granules
Eccentric nucleus that looks oval or kidney-shaped
Macrophages
EM
Many lysozomes
Well developed Golgi
Prominent rER
Macrophages
Function
- Ingestion and digestion of foreign particles by lysozomes
- Antigen processing and presentation
- Destruction of old red blood cells.
- Secretion of substances that participate in defensive function
- Activation of the immune response
What happenes when macrophages are activated:
- Possessing more microvilli and lamellipodia
- Exhibit more locomotion
- Increase their capacity for phagocytosis
- Increase in intracellular digestion
- Enhanced lysosomal activity
- Secretion of substances that participate in inflammation and repair (Collagenase)
Under chronic inflammatory conditions, what happens to the macrophages?
Greately enlarge and become epitheliod cells or fuse to form a giant multinucleated macrophage
Mast cells
Origin, shape, cytoplasm, nucleus
From stem cells in the bone marrow
Oval to rounded cells
Cytoplasm filled with basophilic corase granules
Small, spherical, centrally located nucleus which is obscured by cytoplasmic granules
Mast cells
EM
Well-developed Golgi
Heterogenous membrane-bound granules
Few mitochondria
rER
Mast cells
Stain
Metachromatic stain with toulidine blue
Difference between primary and secondary mediators of inflammation
Primary mediators are synthesised and stored inside the mast cel while secondary mediators are synthesised and immediately released
Primary mediators examples:
Heparin
Histamine
Neutral proteases
ECF-A (eosinophil chemotactic factor of anaphylaxis)
Secondary mediators examples:
Leukotrienes
SRS-A (Slow reacting substance of anaphylaxis)
Mast cell
Function
Synthesis, storage and release of chemical mediators of inflammation
Inflammation definition
Localized reddness, hotness and swelling
Histamine
Functions
- Dilated blood capilaries and increases their permiability
- Causes contraction of smooth muscles (mainly bronchioles)
Leukotrienes functions
Produce slow contraction of smooth muscles
EFC-A function
It is anticoagulant
Release of mast cells contents produces an allergic reaction known as
Immediate hypersensitivity reaction (anaphylactic shock)
Process of anaphylaxis
1-The first exposure to antigen (bee venom or tetanus antitoxin) results in production of IgE by plasma cells
2- IgE binds to the surface of mast cells
3- A second exposure to the antigen results in binding of the antigen to the IgE on the mast cell surface
4- This event triggers the release of mast cell granules liberating histamine, heparin, leukotrienes and ECF-A
Plasma cell
Origin, shape, cytoplasm and nucleus
From B-lymphocytes from the bone marrow
Large ovoid cells
Basophilic cytoplasm with clear -ve Golgi image near the nucleus
Spherical, eccentric nucleus with compact corase chromatin alternating with light areas giving a cartwheel/ clock-face appearance
Plasma cell
EM
Rich in rER
Well developed Golgi and centriole are present juxtanuclear
Sites of plasma cells
Numerous in sites subjected to penetration by bacteria (Respiratory tract and intestine)
Areas of chronic inflammation
Plasma cells
Function
Synthesis of antibodies
Antibody defenition
Antibodies are specific gobulins produced in response to penetration by antigen
Each antibody is specific for one type of antigen
Leukocytes
sites and examples
They migrate from blood to CT across capilaries and venules
They are neutrophils, eosinophils, basophiles and lymphocytes
CT proper examples
Loose connective tissue
Dense connective tissue (regular and irregular)
CT with special properties examples
- Adipose
- Elastic
- Mucous
- Reticular
- Hematopoietic
Supporting CT examples
Cartilae
Bone
Loose (areolar) CT
sites
- Fills space between fibres and muscle sheathes
- Papillary layer of dermis and hypodermis
- Supports epithelial tissue of serous membranes (Pleura, peritoneium, pericardium), mucous membranes and glands
- Ensheathes the blood and lymphatic vessels
Dense irregular CT
sites
Reticular layer of the dermis
Capsules of spleen, lymph nodes, liver, perichondrium and periosteum
Dense regular CT
Sites
Tendons
Liagments
Yellow elastic tissue
Sites
- Ligaments of vertebral column (Ligmentum flava and ligmentum nuchae)
- True vocal cords
- Elastic lamina of arteries
- Suspensory ligaments of penis
Reticular CT
Sites
It forms the framework of all parenchymatous tissue:
- Myeloid tissue (bone marrow)
- Hematopoitic organs
- Liver
- Lymphoid organs (lymph node, lymph nodules, spleen)
Mucoid CT
Sites
- Umbilical cord (Wharton’s jelly)
- Pulp of young tooth
- Vitreous humor of the eye
Unilocular adipocyte
Sites
Present throughtout the human body except:
- eyelids
- penis
- scrotum
- auricle of external ear except the lobule
Mulitlocular adipocytes
Sites
In hibernating animals
In human embryo and newborns in (neck, axilla and mediastinum)
