Connective Tissue

Areolar Connective Tissue

Structure

Abundant viscous ground substance; few collagen and elastic fibers; scattered fibroblasts; many blood vessels

Function

Protects tissues and organs; binds skin and some epithelia to deeper tissue

Location

Papillary layer of the dermis (skin); subcutaneous layer (deep to skin); surrounds organs, nerve cells, some muscle cells, and blood vessels

Adipose Connective Tissue

Structure

Closely packed adipocytes; nucleus pushed to edge of cell by large fat droplet; contains many blood vessels

Function

Stores energy; insulates, cushions, and protects

Location

Subcutaneous layer; surrounds and covers some organs

Reticular Connective Tissue

Structure

Viscous ground substance; meshwork of reticular fibers, leukocytes, and some fibroblasts

Function

Provides stroma (supportive framework) to lymphatic organs

Location

Spleen, lymph nodes, and red bone marrow

Dense Regular Connective Tissue

Structure

Densely packed, parallel arrays of collagen fibers; fibroblasts squeezed between layers of fibers; scarce ground substance; limited blood supply

Function

Attaches bone to bone (most ligaments) as well as muscleto bone (tendons); resists stress applied in one direction

Location

Tendons (attach muscle to bone); ligaments (typically attach bone to bone)

Dense Irregular Connective Tissue

Structure

Collagen fibers randomly arranged and clumped together; fibroblasts in spaces among fibers; more ground substance than in dense regular connective tissue; extensive blood supply

Function

Withstands stresses applied in all directions; durable

Location

Most of dermis of skin; periosteum covering bone; perichondrium covering cartilage, epineurium covering nerves, epimysium covering skeletal muscle, some organ capsules

Elastic Connective Tissue

Structure

Predominantly composed of elastic fibers; fibroblasts occupy some spaces between fibers

Function

Allows for stretching and recoil

Location

Walls of elastic arteries (such as the aorta), trachea, vocal cords

Hyaline Cartilage

Structure

Glassy-appearing matrix; irregularly arranged chondrocytes in lacunae

Function

Provides support; forms most of fetal skeleton

Location

Tip of nose; trachea; most of larynx, costal cartilage; both the epiphyseal (growth) plates and articular ends of long bones; most of fetal skeleton

Fibrocartilage

Structure

Readily visible, numerous, parallel collagen fibers with limited ground substance; large chondrocytes in lacunae

Function

Resists compression; acts as shock absorber in some joints

Location

Intervertebral discs; pubic symphysis; menisci of knee joints

Elastic Cartila

Structure

Abundant elastic fibers that form weblike mesh; closely packed chondrocytes in lacunae

Function

Maintains shape while permitting extensive flexibility

Location

External ear; epiglottis of larynx

Bone

Structure

Calcified extracellular matrix containing osteocytes trapped in lacunae; compact bone organized in osteons (concentric lamellae arranged around a central canal); spongy bone is a meshwork that has a different organization from compact bone; well vascularized

Function

Provides levers for body movement, supports soft structures, protects organs, stores calcium and phosphorus; spongy bone contains hemopoietic tissue and is the site for hemopoiesis

Location

Bones of the body

Blood

Structure

Contains formed elements (erythrocytes, leukocytes, and platelets); dissolved protein within a liquid ground substance called plasma

Function

Erythrocytes transport respiratory gases (oxygen and carbon dioxide); leukocytes help protect the body from infectious agents; and platelets help with blood clotting. Dissolved protein fibers coalesce and assist with blood clotting. Plasma transports nutrients, wastes, and hormones throughout the body.

Location

Primarily within blood vessels and in the heart

Lymph

Lymph fluid is found within lymph vessels and derives from interstitial fluid. It is mostly water and dissolved solutes and typically no cellular components.