Connective tissue 


Connective tissue plays a crucial role in supporting, binding, and protecting various tissues and organs in the body.

Connective Tissue

Characteristics:


  • Consists of cells within a large 

    extracellular matrix (ECM). 

  • Cells are distant from each other.

  • They can divide & replicate and rearrange, but NOT as

   rapidly as epithelial cells.

  • They tell the cells how to act

  • the body creates to live within

  • Most types of connective tissue have a good blood supply.

  • Made up of many different cell types.

What is the Ground Substance?


  • Gelatinous material.

  • Transparent & colorless.

  • Fills the spaces between fibers and cells in connective tissues.

  • Mainly composed of sugars 

   and proteins.

  • Provides a place for the storage of  water and a medium for diffusion to   take place between cells.

Types of Connective Tissue Fibers:


  1.   Collagenous (Collagen)

  • Composed of collagen (protein). ← Amino acids that line up

  • Has great tensile strength.

  • Is only slightly elastic.

  • Makes up bones, tendons, and ligaments.

  • thick and strong

  • can be found in skin and hair

2.  Elastic


  • Composed of elastin (protein).

  • Very elastic, and much weaker than collagen.

  • Comprises your vocal cords and air passageways of your lungs.

  • can be found in the lungs, the skin's dermis, the vocal cords

3.  Reticular


  • Composed of very fine collagenous fibers.

  • Forms a support network.

  • Acts as a supportive mesh for soft tissues such as liver, bone marrow, and organs within the lymphatic system.

  • Found in organs


Connective Tissue Functions:


  • Protection for internal organs.

  • Structural support.

  • Connection & Binding  (Tendons connect muscle to bone, and ligaments connect  bones to other bones).

  • Stores nutrients such as calcium & phosphorus.

  • Produces red blood cells.

Connective Tissue Functions continued:


  • Stores energy as fat (White Fat).

  • Helps fight against infection (Immune cells).

  • Tissue repair after injuries.

  • Transports nutrients through direct diffusion between organs and other tissues.

  • Heat generation (brown fat; breaks down glucose to produce heat to help with body temperature regulation).

  • Provides a supportive framework in many organs.

Types of Cells found in Connective Tissue:

  1.   Fixed Cells → make EM


  • Stay in one place and certain cells have stable numbers, and some move

  • Produce & secrete all parts of the ECM.

Two Forms:

a.  Fibroblasts → immature cells of connective tissue

  • Large & star-shaped; is the most common form.

  • Secrete all sugar and protein portions of the ECM.

     Other Examples:

1. Osteocytes – found in bone. → make bone

2. Chondrocytes – found in cartilage. → make cartilage

b. Mast Cells → produce histamine and heparin


  • A type of white blood cell found in

      connective tissue.

  • Usually found near blood vessel walls.

  • Important in homeostasis.

Functions:

  1. Release heparin (prevents

blood clotting and can be deadly)

  1. Release histamine (Causes an Allergic reaction &/or inflammation and can also make you sneeze)

2.  Wandering Cells

  • Cells in connective tissues that are NOT fixed in one location.

  • These cells can travel throughout the body and act as scavenger cells against infection.

  • The number of these cells can change in response to infection

Examples:

a.  Macrophages

-    These cells can travel through the body.

  • The number of these cells can change in response to infection.

  • Phagocytosis: the process by which a cell envelopes and destroys another particle or cell

Examples of Connective Tissues:

  1.  Connective Tissue Proper


a. Areolar (Loose Connective Tissue)- FIbroblasts

  • Contains all cell types and fiber 

     components that we’ve already 

     discussed. 

     (Collagen, Elastic, & Reticular)

  • Forms a delicate, thin membrane 

     throughout the body. 

     (Skin, Organs, Blood Vessels)

  • Binds body parts together such as 

     the skin and underlying organs.

-   Has a good blood supply.

b.  Adipose  (Loose Connective Tissue)- Fibroblasts


  • Connective tissue composed mainly of fat (Energy) storage cells (white and brown).

  • Has little to no ECM.

  • Cushions joints and protects organ tissues.

  • Found below the skin, around joints, and pads organs.

-   Comprised mainly of collagen fibers.

c.  Reticular  (Loose Connective Tissue)- Fibroblasts


  • Provides a mesh-like, supportive framework for soft tissues, such as the spleen and liver.

  • Comprised mainly of reticular fibers.

d.  Regular (Dense)- Fibroblasts


  • Made of strong collagen fibers that bind body parts together.

  • Found in ligaments and tendons.

  • Has a poor blood supply, so healing is slow.

e.  Irregular (Dense)- Fibroblasts


  • Has a random pattern of connective collagen fibers.

  • Allows greater strength in more directions overall than dense tissue.

  • Gives arterial walls their strength to stretch, then regain their shape. -Dermal layer of skin


f.  Elastic Connective- FIbroblasts


  • Found in areas where a strong, elastic tissue is needed.

  • Examples: Found along the attachment sites for the spinal vertebrae, and surrounding the heart.

Examples of Connective Tissues:

2.  Supportive Connective Tissue → holds together


a. Hyaline Cartilage - Chondrocytes

  • Most common type of cartilage.

  • Made up mainly of fine collagen fibers.

  • Collagen makes chondrocytes

  • Found at the ends of bone, nose cavity, and supporting rings of the respiratory system. → like tunnel

  • The embryonic skeleton is hyaline cartilage

Chondrocytes in this tissue eventually die due to the lack of a blood supply.


  • As cartilage dies, bone can start to form.

  • Spaces (lacunae; like a cocoon) can also provide a frictionless surface for joints and protect bones.

  • can NOT make new cartilage

  • Rubbery surface so bones don’t rub against each other

b.  Fibrocartilage- Chondrocytes


  • Tough tissue containing many thick, fibrous collagenous fibers.

  • Shock absorbers between vertebrae, knees, and the pelvic girdle.

c.  Elastic Cartilage- Chondrocyte’/s


  • Very flexible.  Makes up the ears and larynx.

  • Used for flexible support.

  • Main fibers are Elastin.

d.  BONE- Osteocytes


  • Hardest connective tissue.

  • Protects internal organs and supports the body.

  • Produces blood cells which makes blood

  • Attachment point for muscles.

MATRIX:

  • Contains mineralized (Ca&P) collagen & elastin fibers.

Bone Structure:


a. Central Canal

  • Contains nerves & blood vessels.

b. Canaliculi

  • Very small tubes that allow for movement between cells.

c. Lamellae 

  • The multiple layers within bone.

d. Osteocytes → form bone arround themselves

  • Mature bone cells that help repair & maintain bone homeostasis.

Examples of Connective Tissues:

3.  Fluid Connective Tissue


a. Blood

  • Only connective tissue with a full liquid matrix.  Has NO fibers! but has protien

  • Red blood cells are used for the transport of oxygen.

  • Platelets-prevent blood loss

  • White blood cells are used to fight off infection. → immune system and has plasma

  • Plasma is made up of water, sugar, fat, protein, and salts.