Connective tissue

Connective tissue is a diverse group of tissues that play a fundamental role in supporting, binding, and protecting other tissues and organs in the body. It is characterized by an extracellular matrix that provides structural and biochemical support to surrounding cells.

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.