Chapter 4: Connective Tissue Flashcards
How is a functionally integrated body maintained?
The connective tissue forms a linkage with the epithelial, muscular, and nervous tissues to maintain a functionally integrated body.
Connective tissue origin
Middle mesodermal layer of the embryonic tissue. From this layer, mesenchymal cells migrate throughout the body, giving rise to connect tissue cells.
What are the characteristics of connective tisssue?
- Formed of widely separated cells with a large amount of Intracellular matrix.
- Penetrated by blood vessels, lymphatics, and nerves.
What are the functions of the connective tissue?
- Provides structural support for tissues and organs.
- Serves as medium of exchange of metabolic wastes, nutrients, and oxygen between blood and body cells.
- Site of fat storage.
- Defense and protection of the body by their phagocytic and cells of immunity.
What are the components of connective tissue?
- Cells
- Matrix: soft, rubbery, solid, and fluid.
Solid matrix
Bones
Rubbery matrix
Cartilage
Fluid matrix
Blood
Soft matrix
Connective tissue proper.
Connective tissue proper is divided into?
Cells:
1. Resident cells
2. Transient cells
Matrix:
1. Fibers
2. Ground substances
Resident Cells of C.T. Proper
- Fibroblast
- Fat cells (adipose)
- Mast cells
- Macrophages
- Reticular cells
- Pericytes
- UMC
Transient Cells of C.T. Proper
- Plasma cells
- Leukocytes
Resident cells
Long lived cells
Transient cells
Short lived
Matrix fibers of C.T. Proper
- Collagen
- Elastic
- Reticular
UMC site in embryo
Unspecialized stem cell
UMC site in adults
Remain undifferentiated in certain areas to act as a life-long source for some cells:
In the bone marrow: blood cells.
Around blood vessels: pericytes (perivascular cell).
UMC LM
- Small branched cell.
- Pale basophilic cytoplasm.
- Central large oval pale nucleus with visible nucleoli.
UMC EM
- Many free ribosomes.
- Euchromatic nucleus.
UMC function
Can divide and differentiate into other types of C.T cells.
Pericyte (perivascular) cells origin
UMC
Pericytes site
Adult mesenchymal stem cells around blood capillaries.
Pericyte LM
- Branched with long process.
- Pale basophilic cytoplasm.
- Central large oval pale nucleus with visible nucleoli.
Pericytes EM
- Many free ribosomes.
- Euchromatic nucleus.
- Network of myosin and actin.
Pericytes function
In injury: can divide and differentiate into endothelium, fibroblast, and smooth muscle cells.
By contraction: vasoconstriction.
Fibroblasts Origin
UMC and Pericytes
Fibroblasts site
Most common type of C.T. Cells. Found in nearly all types of C.T. Proper.
Fibroblasts shape
Active fibroblasts and inactive fibroblasts (fibrocytes).
Active fibroblasts LM
- Branches of many long thin processes.
- Deep basophilic cytoplasm.
- Central large oval pale nucleus with prominent nucleolus.
Inactive fibroblasts LM
- Smaller spindle with few processes.
- Paler basophilic cytoplasm.
- Darker nucleus.
Active fibroblasts EM
An image of a protein synthesizing cell:
1. Many mitochondria
2. Well developed Golgi apparatus
3. Well developed rER
4. Euchromatic nucleus.
Inactive fibroblasts EM
- Less mitochondria, Golgi apparatus, and rER.
- Nucleus with more Heterochromatin.
Active fibroblasts functions
- Synthesis of C.T. fibers.
- Synthesis of ground substances of the matrix.
- Production of growth factors for cell growth and differentiation.
- Healing and repair of C.T. after injury.
Functions of inactive fibroblasts
- In injury it becomes active, wound healing.
- Continuous slow turnover of extracellular components to maintain C.T.
Adipose cell other names
Fat cell, adipocyte.
Origin of adipose cell
UMC
Site of adipose cell
- Unilocular adipose cell
- White adipose C.T. - Mulilocular adipose cell
- Brown adipose C.T.
White adipose LM
- Large oval ( 50-150 micrometers).
- Fat is stored as one large droplet ( contains dissolved caretnoids) displacing the cytoplasm and nucleus peripherally.
- Fat is removed during H and E which gives it a signet ring appearance.
- Peripheral flattened nucleus.
- Special stain: Sudan III (orange).
Brown adipose LM
- Smaller.
- Fat is present as multiple small droplets.
- No signet ring appearance.
- Mostly eccentric, round nucleus.
- Pigmented ( Brown color).
White adipose EM
- Abundant sER.
- Few mitochondria.
- Large single electron dense fat droplet.
Brown adipose EM
- Less sER.
- Many mitochondria ( rich in cytochrome oxidase).
- Multiple small electron dense fat droplets.
Functions of white adipose
- Synthesis and storage of fat.
- Support of organs such as the kidney.
- Heat insulation.
- Endocrine function: secrete leptin hormone, which inhibits food intake and stimulates metabolic rate and loss of body weight.
Brown adipose functions
- Thermogenesis: breakdown of fat to release heat via thermogenesis protein found in their mitochondria.
Reticular cell origin
UMC
Reticular cell site
At Roma of glands and organs such as the lymph nodes, endocrine glands, and spleen.
Reticular cell LM
- Small Stella tea with many long thin processes.
- Pale basophilic cytoplasm.
- Central pale round nucleus with prominent nucleolus.
Reticular EM
- Variable number of organelle depending on its activity.
- Processes are joined by cell junctions.
Reticular cell functions
- Supportive network of reticular fibers.
- Secretion of reticular fibers.
- Turns phagocytic when stimulated by antigen.
- Antigen presenting cell to activate lymphocytes.
Macrophages origin
Monocytes
Macrophages site
In C.T. Like bone marrow, bone, brain, liver, lung, lymphoid tissue.
Macrophages LM
- Large irregularly shaped.
- Pale basophilic cytoplasm.
- Eccentric, dark kidney shaped nucleus.
- Special stains:
- vital sign: tarpan stain or India ink. - Stain is phagocytoses by the cell.
Macrophage (histiophage) EM
- Cell membrane shows pseudopodia.
- Rich in lysosomes, phagocytosed particles and residual bodies.
- Prominent Golgi apparatus, few rER.
- Heterochromatic nucleus.
Macrophages functions
- Phagocytosis and destruction of foreign particles, microorganisms, and dead cells (debris).
- Multinucleated foreign body giant cell is formed by their fusion to engulf large particles.
- Antigen presenting cell to activate lymphocytes.
- Destruction of old RBC’s (liver and spleen).
Mast cell origin
UMC
Mast cell site
- Loose C.T around blood vessel.
- Loose C.T. Under epithelium in lungs and digestive tube.
Mast cell LM
- Large oval cell shape.
- Basophilic cytoplasm with basophilic granules.
- Central spherical pale nucleus.
- Specific stain: granules stained metachromatically (purple or red) by toluidine blue.
Mast cell EM
- Well developed Golgi apparatus.
- Many mitochondria.
- Few rER.
- Electron dense membrane bound granules (secretory vesicles).
Mast cell functions
- Carries surface receptors for IgE and responsible for secretion of:
- Heparin: anticoagulant.
- Histamine: vasodilation and increased permeability.
- Leukotrienes: smooth muscle contraction in bronchial tree (which lead to) bronchial asthma.
- Eosinphil chemotactic factor: attracts eosinophils to allergic site.
Heparin
Anticoagulant
Histamine
Vasodilation and increased permeability.
Leukotrienes
Smooth muscle contraction in bronchial tree (which leads to) bronchial asthma.
Eosinophil chemotactic factor
Attracts eosinophil to allergic site.
Plasma cell origin
B-lymphocyte (make) plasma.
Plasma cell sites
Numerous in lymphoid tissue.
Plasma cell LM
- Large oval cell in shape.
- Deep basophilic cytoplasm with negative Golgi image.
- Eccentric spherical nucleus containing heterochromatin alternating with lighter areas of euchromatin. This causes a cart wheel or clock face appearance.
Plasma cell EM
Picture of protein forming cell:
1. Rich in rER.
2. Well developed Golgi apparatus.
3. Many mitochondria.
4. Euchromatic nucleus.
5. No secretory granules.
Plasma cells function
Synthesis and secretion of antibodies.
How do allergic reactions occur?
In some people, immune system recognizes harmless antigens (allergens) as foreign bodies. Binding of allergens to IgE on surface of mast cells triggers the release of its secretions leading to allergic reaction or hypersensitivity reaction.
How can allergic reactions manifest?
- Erythema and itching (skin).
- Runny nose.
- Bronchospasm (respiratory passages).
- Vomiting.
- Diarrhea.
- Abdominal cramping (gastrointestinal tract).
What can massive discharge of mast cells result in?
It can cause a life-threatening anaphylactic shock which will lead to severe vasodilation and increased permeability of blood cells. This results in severe hypotension.
Extravasted leukocytes
Leave blood through capillaries to perform there immunity functions.
Undifferentiated cells
UMC and Pericytes
C.T. Forming cells
Active fibroblasts, inactive fibroblasts (fibrocytes), and reticular cells.
Fat containing cells
Unilocular and multilocular adipocytes.
Cells responsible for immunity and defense
Macrophages, mast cells, plasma cell, and leukocytes.
What are fibers formed of?
Protein molecules polymerized to form thin threads.
Collagen fibers structure
Type 1 collagen protein
Collagen fibers synthesis
- Mainly fibroblasts
- Chondroblast (in cartilage)
- Osteoblasts (bones)
Collagen fibers LM
- Wavy branching bundles formed of non branching fibers.
- colorless in fresh sections (white when condensed e.g. tendons).
Collagen fibers staining
- Eosin: pink
- Mallory’s Trichrome: blue
- Van gieson: red
Collagen fibers characters
- The strongest fibers
- Flexible but Inelastic
Collagen fibers functions
- Gives strength
- Resist stretching
Elastic fibers structure
Elastin protein
Elastic fibers synthesis
- Mainly fibroblasts
- Chondroblast
- Smooth muscle cell
Elastic fibers LM
- Single, thin and branching.
- Yellow in fresh sections.
Elastic fibers stains
- Eosin: pink.
- Orcein: brown.
- Von Gieson: yellow.
Elastic fibers characters
Stretch and recoil.
Elastic fibers functions
Give elasticity
Reticular fibers structure
Type III collagen
Reticular fibers synthesis
- Mainly fibroblasts
- Reticular cells
- Smooth muscle cells
Reticular cells LM
Fine fibrillar network (spider net)
Reticular cells staining
- H and E not visible.
Due to their high sugar content, they can be stained by: - Silver: Brown.
- PAS: Red.
Reticular cells characters
Loose flexible supporting network.
Reticular cells functions:
Forms a network in the stream of organs as spleen, lymph nodes, and liver.
Vitamin C deficiency (scurvy)
Due to defective collagen synthesis.
It is characterized by:
1. Unhealed wounds.
2. Bleeding gums.
Keloid
Local swelling caused by abnormal healing processes leading to increased deposition of collagen in scars of skin.
Most common types of collagen
Type 1,2,3,4,7.
Type 1 main character
Arranged in bundles.
Type 1 main sites
- C.T proper: tendon.
- Bone: capsule of organ.
Type 1 cells of origin
- Fibroblasts
- Osteoblasts
Type 2 main character
Fine fibers
Type 2 main sites
Cartilage
Type 2 cells of origin
Chondroblast
Type 3 main character
Reticular fibers
Type 3 main sites
Stroma of some organs.
Type 3 cells of origin
- Fibroblasts
- Reticular cells
- Smooth muscle cells
Type 4 main character
In the form of granules.
Type 4 main sites
Basement membrane associated with epithelium.
Type 4 cells of origin
Epithelial cells
Type 7 main characters
Anchoring fibers
Type 7 main sites
Basement membrane associated with epithelium.
Type 7 cells of origin
Fibroblasts
Types of C.T proper fibers
- Loose: abundance of ground substances and tissue fluid in which cells and fibers are scattered.
- Dense: abundance of fibers with fewer cells than in loose type.
Loose
- Loose areolar C.T.
- Adipose C.T
- Reticular C.T
- Mucoid C.T
Dense
- White fibrous C.T.
- Yellow elastic C.T.
Loose (areolar) C.T. Structure
Most common type:
1. All types of C.T. Cells.
2. All types of fibers (mainly collagen bundles).
3. Most abundant matrix.
Loose areolar C.T. Characteristics
- Loose: potential cavities (areolae) which can accommodate a large amount of fluid or gases.
- Flexible and well vascularized.
Loose areolar C.T. Sited
Found everywhere in the body except the brain:
1. Filling spaces between organs.
2. Papillary layer of dermis of skin.
3. Mucosa and serous membrane.
4. Around blood vessels and nerves.
Loose areolar C.T. Functions
- Exchanging of nutrients to and from blood vessels.
- Binding structures together.
- Limiting spread of infection.
Reticular C.T. Structure
- Reticular cells.
- Fine network of reticular fibers.
- Moderate amount.
Reticular C.T. Characters
Delicate type
Reticular C.T. Sites
A supporting framework stroma of organs Eg. Lymph nodes, liver, spleen etc
Reticular C.T. Functions
Supportive
Reticular C.T. Staining
Silver (Ag): brown, black.
Mucoid C.T. Structure
- Mainly fibroblasts.
- Fine collagen reticular fibers.
- Large amount of soft, jelly-like, ground substances rich in mucus and Hyaluronic acid.
Mucoid C.T. characters
Jelly-like in which ground substances predominates.
Mucoid C.T. Sites
- Umbilical cord (Wharton’s jelly).
- Vitreous humor of the eye.
- Pulp of teeth.
Mucoid C.T. Functions
Supportive
Adipose C.T. Structure
- Fat cells predominate over other components.
- Reticular fibers form a fine network that supports individual fat cells and bind together.
- Collagen fibers divide this tissue into incomplete lobules.
Types of adipose C.T.
White adipose C.T. And Brown adipose C.T.
Whit adipose C.T. Characters
- Fat cells are Unilocular.
- Less vascularity + presence of carotenoids dissolved in fat droplets which gives them the white color.
- Affected by diet and hormones.
Brown adipose C.T. Characters
- Fat cells are multilocular.
- Higher vascularity and cytochrome pigments in mitochondria which gives the brown color.
- Affected by hormones not diet.
White adipose C.T. Sites
Widely distributed all over the body:
1. Under the skin especially females as in gluteal region and abdominal wall.
2. Mammary glands.
3. Mesentry.
4. Around kidney or other organs.
Brown adipose C.T. Sites
- Present in large amounts in humans during fetal life and newborns.
- Lost during childhood to be replaced gradually by white type.
- In adults, it is localized in certain areas:
a. Interscapular
b. Mediastinal
c. Axillary regions
White adipose C.T. Functions
- Heat insulation.
- Storage of fat.
- Support organs as the kidney.
- Secretion of leptin.
- Giving the skin its contour.
Brown adipose C.T. Functions
- Heat generation (thermogenesis) in newborns.
White fibrous C.T. Cells
Fibroblasts
White fibrous C.T. Fibers
Collagen fibers packed in bundles.
White fibrous C.T. Matrix
Minimal amount.
White fibrous C.T. Characteristics
- Very dense due to great predominance of collagen fibers with few cells which leads to white color in fresh state.
- Resistant and less flexible.
Types of white fibrous C.T.
Regular white fibrous C.T. And irregular white fibrous C.T.
Regular white fibrous C.T.
Regularly arranged collagen bundles with fibroblasts arranged in rows in between.
Irregular white fibrous C.T.
Irregularly arranged collagen bundles scattered fibroblasts.
Regular white fibrous C.T. Sites
- Tendons.
- Cornea.
Irregular white fibrous C.T. Sites
- Reticular layer of dermis of skin.
- Ligaments.
- Sclera of the eye.
- Capsule of organs.
Regular white fibrous C.T. Function
Withstanding stretch in one direction.
Irregular white fibrous C.T. Functions
Withstanding stretch in different directions.
White fibrous C.T staining
- Eosin: pink.
- Mallory’s trichrome: blue.
- Van gieson: red.
Yellow elastic C.T. Cells
Fibroblasts
Yellow elastic C.T fibers
Condensed parallel elastic fibers.
Yellow elastic C.T. Matrix
Small amount
Yellow elastic C.T. Characters
- Dense type with great predominance of elastic fibers which gives it the yellow color in fresh state.
- Great elastic power (recoil when stretched).
Yellow elastic C.T. Sites
- Aorta and large arteries.
- Trachea, bronchi, bronchioles, and around aveoli.
- Vocal cords.
- Some ligaments:
a. Ligamentum flavum: joining the vertebrae.
b. Ligamentum nuchae: at the back of the neck.
c. Suspensory Ligaments of penis.
Yellow elastic C.T. Functions
Great elastic power.
Yellow elastic C.T. Staining
- Eosin: pink.
- Orcien: brown.
- Von Gieson: yellow.