Connective tissueConnective tissue

TYPES:

1-CT. proper.

2.Specialized CT (cartilage,

bone and blood).

Connective tissue properConnective tissue properComponents of CT:1-Cells.2-Extracellular matrix (ground substances and

fibers).Functions of CT:a. Structural supportb. A medium for exchange.c. Helps in defense & protection of the body.d. A site for storage of fat.

Extracellular MatrixExtracellular Matrix I-Ground substanceIt is a hydrated, amorphous material that is

composed of: Glycosaminoglycans, proteoglycans and adhesive glycoproteins.

II-Fibers Collagen fibersCollagen fibers, are inelastic and possess

great tensile strength. Each fiber is composed of fine subunits called tropocollagen molecule.

Most of the fibers show axial periodicity by EM.

There are six major collagen types: Type I: in CT proper, bone, dentin.

Type II: In hyaline and elastic cartilage.Type III: reticular fibers.( stroma of spleen

& lymph nodes)

Elastic fibers:Elastic fibers:Structure of Elastic Fiber the fiber branch

and anastomose with each other they run singly and not in bundles but forming a membrane.

Stretchable Fibers.

Collagen type ICollagen type I

CT.CellsCT.Cells 1.Fibroblasts1.Fibroblasts

2.Adipose cells.2.Adipose cells.

3.Pericytes.3.Pericytes.

4.Mast cells.4.Mast cells.

5.Macrophages.5.Macrophages.

6.Plasma cells.6.Plasma cells.

7.leukocytes.7.leukocytes.

They are the most abundant CT. cells and derived

from undifferentiated mesenchymal cells.Types: 1- Active fibroblasts: are elongated, fusiform cells

with dark-staining cytoplasm rich in RER with large ovoid nucleus containing well-defined nucleolus.

2- Inactive fibroblasts (fibrocytes): are smaller and are more ovoid with more acidophilic cytoplasm.

• Fibrobalsts are responsible for the synthesis of almost of extracellular matrix.

• can close wound during injury.

I- Fibroblasts I- Fibroblasts

II-Adipose cells (fat cells or adipocytes):II-Adipose cells (fat cells or adipocytes):They are derived from undifferentiated mesenchymal cells.They are fully differentiated and do not undergo cell division.There are 2 types: A-UnilocularA-Unilocular fat cells, form white adipose tissue: they are

large cells, they store fat as one droplet, which enlarge pushing the cytoplasm and the nucleus peripherally against cell membrane (signet-ring appearance). They have few mitochondria. The fat droplet is not bounded by a membrane.

Present in: Present in: under the skin especially in females, it is more considered in the

mammary glands and gluteal region.

B-Multilocular adipocytesB-Multilocular adipocytes, form brown adipose tissue:Are small cells with multiple fat droplets, central spherical

nucleus and many mitochondria.Present In: new born.* They function in the synthesis, storage and release of fat.

AdipocytesAdipocytes

III- PericytesIII- PericytesThey surround capillaries and small venules.They have multiple processes that wrap around the

endothelium of blood capillaries and small venules.

Function:Function:1.Important in the healing of CT of blood vessles

where ever wound presents2. give raise to smooth muscle cell3. can modified for smooth muscle cells which can

contract.

IV. Mast cells:IV. Mast cells:

Their cytoplasm is rich in membrane-bound granules that stained metachromatically with toluidine blue.

The granules contain heparin, histamine.

Histamine causes vasodilatation and increase permeability of blood vessels. It causes bronchospasm and increase mucus production.

Mast CellMast Cell

V- MacrophagesV- Macrophages

Derived from blood monocytes after migrate from blood from C.T.

Some are fixed and others are transient .They are irregular in shape due to the

present of filopodia.They have branched cell with many process. Their cytoplasm Is basophilic, prominent

RER, well developed Golgi and an abundance of lysosomes.

They derived from monocytes.

MacrophageMacrophage

VI- Plasma cellsVI- Plasma cellsThey are derived from B-lymphocytes after

exposure to an antigen.They secrete antibodies.They are large ovoid cells with intensely basophilic cytoplasm that is rich in RER and Golgi (pale-staining region adjacent to the nucleus that has chromatin radiating out from the center (clock-face appearance).

VII- Leukocytes:VII- Leukocytes:

They are white blood cells that circulate in

blood stream then migrate through

capillaries to enter CT. during

inflammation, invasion by foreign elements

and immune response.

In the present of infection.

Connective tissue properConnective tissue proper1- Loose (areolar CT):1- Loose (areolar CT):It fills in the spaces of the body just deep to

the skin, The loose CT of mucous membranes is

called lamina propria.It is characterized by abundant ground substance and tissue fluid housing the fixed CT. cells, undifferentiated cells and collagen, reticular and elastic fibers.Its ground substance loose.

2. Reticular CT: 2. Reticular CT: Type III collagen is its major component. Collagen forms mesh-like networks It forms the framework of liver, lymph nodes, spleen,

3. Adipose tissue:3. Adipose tissue: It is divided into white (unilocular) adipose tissue and brown (multilocular) adipose tissue. It is rich in blood vessels.

Adipose CT.Adipose CT.

4. 4. Dense CT:Dense CT: It has many more fibers and fewer cells

than ordinary CT.It is formed of three types:

a. Dense irregular collagenous CTa. Dense irregular collagenous CT: it is formed of randomly arranged collagen fibers, few ground substances and fibroblasts scattering between collagen fibers. It form the dermis of skin,

b. Dense regullar collagenous CT: b. Dense regullar collagenous CT: it is composed of coarse collagen bundles that oriented into parallel sheets. It has few ground substances and fibroblasts between collagen bundles.Ex. Tendons.

Dense irregular CT. Dense regular CT

c. Dense regular elastic CT: c. Dense regular elastic CT: it has coarse branching elastic fibers and scattered fibroblasts. Elastic fibers are arranged parallel to one another and form either thin sheets or fenestrated membranes as in large blood vessels (aorta).

Practical slidesPractical slides

Elastic connective tissue