Connective Tissue and Skin

connective tissue

cells separated by a matrix of loosely or densely packed intercellular material. Matrix consists of fibers and of loose or dense ground substance.

Fibroblasts

most abundant, large, star-shaped, produce fibers

Fixed macrophages

irregularly shaped and utilized to engulf invaders and damaged cells

Adipocytes

fat cells, number varies between types of connective tissue

Mesenchymal cells

stem cells, respond to local injury or infection by dividing to produce new cells

Melanocytes

produce melanin (dark brown pigment); common in epithelial tissue but also found in connective tissue; give tissue a dark color and differ in number in individuals

Free macrophages

like fixed macrophages but are free to circulate throughout connective tissues. When within the blood are called monocytes

Mast cells

small, mobile cells found near blood vessels; secrete histamine and heparin to stimulate local inflammation in response to injury/infection

Lymphocytes

migrate throughout body and increase in number where tissue damage occurs; can develop into plasma cells which produce antibodies

Microphages (e.g. neutrophils and eosinophils)

migrate throughout body and respond to chemicals released by macrophages and mast cells. These are also phagocytic

Collagen fibers

relatively thick, thread-like, composed of collagen and occur in long, parallel bundles. Can withstand much force when pulled along axis.

Elastic fibers

thinner and form complex networks; branched. Return to original length after stretching.

Reticular fibers

highly branched and delicate supporting networks. Able to resist forces applied from many directions

Areolar connective tissues

Location: found below epithelium in most parts of the body. Made up of fibroblasts with elastic and collagenous fibers.

Function: strength, elasticity, support

Made up of: collagen, elastic, and reticular fibers arranged randomly

Reticular connective tissue

Resembles areolar tissue but the matrix is made up of only reticular fibers.

Found in bone marrow, spleen, liver, and lymph nodes

Function: forms storma of organs, binds together smooth muscle, filters and removes worn out blood cells in spleen

Made up of: fine interlacing network of reticular fibers

Adipose connective tissue

Has modified fibroblasts which store fat and thus become swollen, pushing the nucleus to the edge of the cell. Widely distributed throughout the body

Function: reduces heat loss through skin, energy reserve, supports and protects organs

Made up of: specialized connective tissue, stores triglycerides in fat droplets in cells

dense regular connective tissue

Thickly packed collagenous fibers in a regular, parallel arrangement. Contains fibroblasts and a few elastic fibers.

Found in: tendons, ligament, aponeuroses, and covering skeletal muscle (deep fasciae)

Function: strong attachment between bodily structures to withstand pulling force along its axis

Made up of: thickly packed collagen fibers

Dense irregular connective tissue

resembles dense regular connective tissue except the collagenous fibers are irregularly arranged. Also contains fibroblasts and a few elastic fibers.

Found in: fibrous capsules of organs and joints, periostea, perichondria, nerve and muscle sheaths, and makes up the dermis

Function: provides pulling strength in several directions

Made up of: tightly packed collagen fibers "irregularly" arranged

Elastic connective tissue

Predominance of elastic fibers with fibroblasts embedded in between.

Found in: walls of the aorta and other blood vessels, in the vocal cords, surrounding respiratory passages, and ligament flava and ligamentum nuchae of spinal column. Often underlies transitional epithelium

Function: stretching of various organs, strong, can recoil

Contains: largely of elastic fibers

Cartilage

a supporting connective tissue. made up of chondrocytes (cartilage cells) surrounded by a semisolid gel-like matrix. Avascular. (note presence of chondrocytes)

Hyaline cartilage

maxtrix of tightly packed collagen fibers not easily seen under light microscope. Clear, glassy appearance.

Found in: tracheal rings, costal cartilages of the ribs, cartilage of nose, larynx and covers bone surfaces at synovial joints

Function: tough but flexible, smooth surface for joints, flexibility, support

Weakest (can be broken)

Fibrocartilage

Matrix is supported by collagenous fibers which are densely packed and regularly arranged. Feather like appearance.

Very tough and durable, strongest of the cartilages

Location: intervertebral discs, makes up the menisci of the knee joint and in the symphysis pubis.

Function: support, join 2 structures together, strength, rigidity

Elastic cartilage

Matrix is supported by elastic fibers which make it resilient and flexible, are less densely packed, and are arranged irregularly. Threadlike network of elastic fibers.

Location: pinna, epiglottis, and auditory canal

Function: strength, elasticity, maintain shape

Bone

a supporting connective tissue; one-third of its matrix consists of collagenous fibers

Blood

a fluid connective tissue

Lymph

also considered a fluid connective tissue

Epidermis

5 layers: deep to superficial

Stratum basale or stratum germinativum

base, cell division

Stratum spinosum

thick layer, slower/less cell division

Stratum granulosum

cells start to die, dead cells give substance (waterproof)

stratum lucidom

only found in thick skin

Stratum corneum

most superficial, thickest layer

Carotene

the yellow pigment of the skin, Vit-A precursor, stratum corneum

Melanin

Formed by melanocytes, protect from UV

thin vs thick skin

Thick skin covers front of hands, bottoms of feet

Thin skin covers rest of the body

Dermis

divided into papillary and reticular regions

blood vessels

cells in dermis need nutrients, helps with temp. regulation

nerve fibers

sensations, protects us

sebaceous glands (sebum)

surrounds hair follicles, make sure hair/skin stay moisturized

sudoriferous apocrine glands

fatty sweat, body odor, groin, armpits, start more at puberty

sudoriferous eccrine gland

pores; hands, face, watery secretion, have them at birth

vellus hair

peach fuzz

terminal hair

Long, coarse, pigmented hair found on the scalp, legs, arms, and bodies of males and females.

arrector pili muscle

goosebumps, generate heat, smooth muscle

Pacinian corpuscles

deep pressure/vibration receptors, looks like an onion on diagram

Ruffini corpuscles

detects twisting, stretching of dermis

Meissner corpuscles

under the s. basale, detect more fine touch movements

Merkel cells (epidermal)

detect fine touch;s. basale