Mammalian Tissue Structure and Function

Epithelial Tissue

Lines surfaces

Connective Tissue

Joins other tissues together

Muscle Tissue

Actively contracts and passively relaxes

Muscle Tissue

Actively contracts and passively relaxes

Simple Epithelium

Single layer of cells; functions in absorption and secretion (ex. Glands or ducts)

Pseudostratified Epithelium

Arrangement of cells make tissue seem multi-layered; functions in mucus secretion and fluid absorption (ex. Respiratory system)

Stratified Epithelium

Two or more layers thick; functions in protection from wear and tear (skin)

Squamous

Cells are flat in shape; line blood vessels, heart, lungs, mouth, and outer layers of the skin

Cuboidal

Cells are cubical in shape; found in tubules of kidney, in glands and their ducts

Columnar

Long and narrow shaped cells; line the intestine and stomach or specialized for sensory organs

Exocrine Glands

Have ducts or tubules

Endocrine glands

Ductless and produce chemical signals

Types of Connective Tissue

Loose, dense, and specialized

Extracellular Matrix (ECM)

Amorphous gel like material made up of proteoglycan molecules (surrounds cells and fibers)

Types of extracellular fibers

Collagen, Elastic, and Reticular

Collagen Fiber

Thick, strong, flexible, inextensible fibrous proteins

Elastic Fiber

Thin, branched, extensible and highly flexible fibers

Reticular Fibers

Small, inelastic, branching fibers which form a mesh-like pattern

Areolar (Loose) Connective Tissue

Skin, mucus membranes, and places where the epithelium is joined to other tissues; securing, cushioning, and protecting organs; reservoir for fluids and solids; abundance of fibroblasts

Adipose Tissue

Throughout the body; cushioning and insulation; stores energy in the form of fat; adipocytes and is derived from lipoblasts

Irregular Dense Connective Tissues

Contains fibers that are not arranged in parallel bundles; comprises a large portion of the dermal layer

Regular Dense Connective Tissues

Collagen fibers are arranged in a parallel manner; found in tendons and ligaments

Cartilage

Specialized connective tissue; chondrocytes and collagenous fibers embedded in pliable gelatinous matrix; providing structure, support, and cushioning at joints; ends of bones, ears, nose, and tracheal reinforcements

Bone

Form of specialized connective tissue; osteocytes surrounded by collagenous fibers and mineralized matrix (calcium salts); movement, support, and protection; bones of vertebrates skeletons

Blood

Specialized connective tissue; classified as a connective tissue because these cells arise in bone; serve as the body’s transport medium; lacks fibers; consist of blood cells in a fluid matrix (plasma)

Red Blood Cells (erythrocytes)

Lack their nuclei at maturity; are the most abundant cell in the blood; function in transport of oxygen

White blood cells (Leukocytes)

Contain nuclei and are slightly larger than RBCs; two categories: granular (cytoplasm contains granules) and agranular (lack granules); function in the immune system

Platelets

Fragments of cells (megakaryocyte) that reside in the red bone marrow; play a role in blood clotting

Granular Leukocytes

Eosinophils (large red granules), Neutrophils (contains a multilobed nucleus and has neutral-colored granules), and Basophils (large blue granules)

Agranular Leukocytes

Lymphocytes (B and T cells) - contain a very large nucleus and crescent shapes cytoplasm; Monocytes (larger than lymphocytes)

Muscle Tissue

Composed of cells that contract when stimulated; originate from the mesoderm; functions in movement; three types: skeletal, cardiac, and smooth

Skeletal (Striated) Muscle

Located in muscles that attach to bones; long, cylindrical cells containing cross striations; bundled closely together in parallel arrays; cells are multinucleated; contraction is under voluntary control

Cardiac Muscle

Present only in the heart; cells have cross striations and branching; intercalated discs join adjacent muscle cells and play a role in synchronizing cardiac contractions; involuntary muscle movement

Smooth (Visceral) Muscle

Located in the walls of many internal organs and blood vessels; cells are not striated; tapered ends (spindle shaped); contain only one nucleus; involuntary muscle movement

Nervous Tissue

Detects stimuli, integrates information, and relays commands for response; consists of excitable neurons and supporting neuroglial cells; conduct nerve impulses

Neurons

Upon stimulation, a nerve impulse travels along the plasma membrane; arrival of the impulse at the nerve ending triggers events that stimulate or inhibit adjacent neurons or other cells