Connective Tissue Types: Structure, Function, and Location
(a) Connective tissue proper: Loose connective tissue, areolar
Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells.
Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays an important role in inflammation; holds and conveys tissue fluid.
Location: Widely distributed under epithelia of the body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries.
(b) Connective tissue proper: Loose connective tissue, adipose
Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have a nucleus pushed to the side by a large fat droplet.
Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs.
Location: Under the skin; around kidneys and eyeballs; within the abdomen; in breasts.
(c) Connective tissue proper: Loose connective tissue, reticular
Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network.
Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages.
Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).
(d) Connective tissue proper: Dense connective tissue, dense regular
Description: Primarily parallel collagen fibers; a few elastin fibers; the major cell type is the fibroblast.
Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction.
Location: Tendons, most ligaments, aponeuroses.
(e) Connective tissue proper: Dense connective tissue, dense irregular
Description: Primarily irregularly arranged collagen fibers; some elastic fibers; the major cell type is the fibroblast.
Function: Able to withstand tension exerted in many directions; provides structural strength.
Location: Dermis of the skin; submucosa of the digestive tract; fibrous capsules of organs and of joints.
(f) Cartilage: Hyaline
Description: Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae.
Function: Supports and reinforces; has resilient cushioning properties; resists compressive stress.
Location: Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx.
(g) Cartilage: Elastic
Description: Similar to hyaline cartilage, but more elastic fibers in the matrix.
Function: Maintains the shape of a structure while allowing great flexibility.
Location: Supports the external ear (pinna); epiglottis.
(h) Cartilage: Fibrocartilage
Description: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate.
Function: Tensile strength with the ability to absorb compressive shock.
Location: Intervertebral discs; pubic symphysis; discs of the knee joint.
(i) Others: Bone (osseous tissue)
Description: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized.
Function: Bone supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat: marrow inside bones is the site for blood cell formation (hematopoiesis).
Location: Bones
(j) Others: Blood
Description: Red and white blood cells in a fluid matrix (plasma).
Function: Transport of respiratory gases, nutrients, wastes, and other substances.
Location: Contained within blood vessels.
(k) Others: Spongy bone
Description: Also known as cancellous bone; lattice-shaped and highly vascular; contains red bone marrow.
Function: Location where blood cells are produced (hematopoiesis).
Location: Proximal to joints, ends of long bones, and vertebra
(l) Others: Lymph
Description: White blood cells: include three major types – T cells, B cells, and natural killer cells.
Function: Immunity
Location: Develop in the bone marrow, found in the lymphatic system and in blood vessels.