Body Tissues

 Histology  4 Tissue Types:  1. Epithelial – (covering)  2. Connective – (support)  3. Muscle – (movement)  4. Nervous – (control)

 Lining, covering, & glandular  Functions: Protections, absorption, filtration, & secretion

 Special Characteristics :  Cells fit closely together to form sheets  Has a free surface (apical surface)  Lower surface – (basement membrane)  Epithelial to connective  Avascular – no direct blood supply  Diffusion  Regenerate easily

 Classification of epithelium  Named according to # of layers & shape of cells at the free surface  Layers:  Simple (1 layer)  Stratified (2 or more layers)  Shape:  Squamous – flat  Cuboidal – cube shaped  Columnar – taller than wide

 Simple Epithelium: absorption, secretion, & filtration  Simple Squamous Epithelium – forms serous membranes (serosae - fluid)  Lines body cavities & organs

 Simple Cuboidal – glands & ducts

 Simple columnar epithelium – forms mucus membranes (mucosae).  Lines cavities open to exterior  Ex. Respiratory Tracts, Digestive Tracts

 Pseudostratified Columnar Epithelium  Lines Respiratory Tract  Ciliated

 Stratified Epithelia–layered; protects  Stratified Squamous Epithelium – most common; high abuse & friction.  Ex. Skin, mouth, esophagus

 Stratified Cuboidal & Stratified Columnar:  Rare; large ducts

 Transitional Epithelia: function is stretching

 Glandular Epithelia: glands; produces & secretes  2 types:  1. Endocrine Glands (ductless)  Directly into the blood stream  Hormones (ovaries, testes, adrenal)  2. Exocrine Glands (ducts)  Sweat, oil  Liver

Answers: A - simple columnar epithelium. B - simple columnar epithelium with cilia. C - stratified squamous epithelium. D - simple squamous epithelium. E - transitional epithelium. F - pseudostratified epithelium. G - stratified squamous epithelium. H - choanocytes I - stratified columnar epithelium with cilia.

 Functions: protection, support, & binding together  Most abundant tissue type  Found everywhere in the body

 Some vascular  Some avascular (cartilage) – heals slowly  Many different types of cells  Extracellular Matrix: non-living substance outside of cell; can be liquid, semisolid or gel-like, or very hard  Examples: Fat (soft); Bone (hard)  Tissue can bear weight, withstand stretching & abrasions.

 Bone (osseous tissue) – vascular  Bone cells surrounded by hard matrix of calcium salts & collagen fibers  Function: protect & support other organs

 Cartilage – avascular  Less hard/more flexible than bone  Hyaline cartilage- voice box; covers end of bone; attaches ribs to sternum; skeleton of fetus  Elastic cartilage- more elasticity. Ex: ears, nose  Fibrocartilage- highly compressible and cushion-like; between vertebrae

 Dense Connective Tissue (fibrous tissue)  Mostly collagen fibers  Forms strong, rope-like structures  Ex: Tendons; Ligaments

 Loose Connective Tissue- Softer & fewer fibers  Areolar Tissue  Soft, pliable tissue that protects & wraps body organs  Universal packing tissue & connective tissue glue that helps hold internal organs together  Edema- areolar tissue soaks up fluid in inflamed area; swells & becomes puffy

 Adipose Tissue – “fat”  Forms subcutaneous layer below skin; insulates & protects from heat & cold.

 Reticular Connective Tissue  Delicate network of fibers  Found in lymph nodes  Ex: Spleen and bone marrow.

 Blood – “vascular tissue”  Blood cells surrounded by blood plasma  Protein fibers in blood  Blood clotting

 Specialized to contract or shorten  Muscle Cells (muscle fibers)

 Skeletal Muscle- (striated muscle)  Attached to skeleton; forms flesh  Voluntary  Cells are long, cylindrical, multinucleate, & striated

 Cardiac Muscle- (heart only)  Has striations, uninucleate; fit tightly together; gap junctions  Involuntary

 Smooth Muscle- (visceral)  No striations, single nucleus & spindle- shaped (pointed at both ends)  Found in walls of stomach, bladder, uterus & blood vessels (hollow organs)  Contracts slowly  Peristalsis – wave-like motion through small intestine  Involuntary

 Cells = Neurons  Function = Irritability & Conductivity A. Tissue Repair (Wound Healing) - Defense at tissue level – skin, mucous membranes, cilia, and acid in stomach glands. - Inflammation – body response to prevent further injury.

- Immune Response – specific to invaders - 2 Ways tissue repairs (depends on tissue type and severity of injury) - Regeneration: replacement of destroyed tissue by same kinds of cells - Fibrosis: repair by dense connective tissue (fibrous) – forms scar tissue

- Process of tissue repair: 1. Capillaries become permeable/allows clotting fibers to seep to injury (bleed) 2. Blood Clot forms/then scab 3. Granulation tissue forms (new skin) 4. Epithelium regenerates/scab falls off (healed) **Scar Tissue cannot function as original cells.

 Growth through cell division  puberty  Replacement of tissue exposed to friction  lifetime  Epithelial Tissue – Mitotic  Connective Tissue – Mitotic (forms scar tissue)  Muscle Tissue – Amitotic after puberty  Nervous Tissue – Amitotic shortly after birth

 Aging – Caused by chemical and physical exposures and genetics, and stress  Neoplasm: abnormal Cell division – multiply wildly – benign or malignant (tumor)  Hyperplasia: enlarged tissue due to local irritant or condition  Ex. Anemia/Bone marrow undergoes hyperplasia to produce more red blood cells  Ex. Breast enlargement during pregnancy

 Atrophy: decrease in size – loss of stimulation  Ex. Muscle reduction from wearing a cast