Body Tissues Ch 3 Part II

INTRODUCTION We start as one cell and work our way to trillions At some point the cells must specialize Differentiation Not a fool proof process Groups of cells with similar structure and function are called tissues

Tissue Types 1. Epithelium- covering 2. Connective- support 3. Nervous- control 4. Muscle- movement Tissues form organs, so in an organ one might see multiple types of tissues

Epithelial Tissue Lining, covering and glandular tissue Forms boundaries between the outside world If it comes in or goes out it probably passes through epithelial tissue Skin protects from dehydration and bacteria, sm intestine absorbs, kidneys filter, sebaceous glands secrete oils

Special Characteristics of Epithelium Most bound tight together by many tight junctions and desmosomes Membranes have an free (apical) surface that can be smooth, or have villi or cillia Deeper surface called the basement membrane. Secreted by connective tissue and epithelium No blood supply of their own Regenerate easily if nourished

Epithelium Classification First name is the relative number of layers Simple- one layer Stratified- more than one layer Second name is for cell shape Squamous- flat like fish scales Cuboidal- cube shaped Columnar- column Stratified are named by the apical surface cells not the cells near the basement membrane

Simple Squamous Epithelia Fit together like floor tiles Filtration and exchange surface due to thickness Lungs and capillaries for exchange Serous membranes that line the ventral body cavity

Simple cuboidal epithelia One layer of cubed cells Glands and their ducts Pancreas, salivary Forms the kidney tubules and covers the ovaries

Pseudostratified Columnar All cells on the basement membrane Different heights give false (pseudo) stratified look Absorption and secretion Cilliated version lines the respiratory system Goblet cells to secrete mucous to keep the lungs clear

Simple Columnar Epithelia Single layer of column cells Often goblet cells that secrete mucous Lines the entire digestive tract from stomach to anus Called mucous membranes if open to the outside surface

Stratified epithelia Two or more layers More durable due to multiple layers Protects Squamous Cuboidal and columnar Transition

Glandular Epithelia A gland makes and secretes a product Proteins and an aqueous solution 2 types 1. Endocrine Gland No connection to surface (ductless)‏ Secrete into blood vessels around the gland  Ex: thyroid, adrenals, and pituitary 2. Exocrine gland Retain their ducts and contact to epithelial surface Sweat, oil, liver and pancreas

Connective Tissue Protects, supports, and connects Found everywhere Unlike epithelia, they have varying degrees of vascularization Cartilage = none Tendons and ligaments = poor Bone = good Better to break a bone than tear your ACL Made of cells and non-living extracellular matrix

Extracellular Matrix Sets connective tissue apart Produced by the connective tissue cells and secreted Made of two elements Ground substance (water based)‏ Fibers 1. Collagen (tensile)‏ 2. Elastic (elasticity)‏ 3. Reticular (skeleton)‏

Types of Connective Tissue Bone (osseous)‏ Bone cells in lacunae surrounded by matrix Ca and collagen for strength to support and protect

Cartilage Softer and more flexible than bone Hyaline cartilage (glass)‏ Fetus Larynx Ribs to sternum Ends of bones Fibrocartilage Vertebral discs Elastic cartilage Ear and tip of nose

Cartilage Types

Dense Connective Tissue Fibroblasts surrounded by collagen fibers Tendons for muscle to bone connection Ligaments for bone to bone Dermis

Loose Connective Tissue Softer and more cells Less matrix 1. Areolar Tissue Cobwebby Holds organs together and in place Reservoir for fluids, salts and wastes Site of localized swelling = edema

Loose connective tissue cont 2. Adipose Tissue = Fat Insulates the body and protects organs Kidneys, eyes Energy storage Hips, abdomen, breasts 3. Reticular Forms the stroma that can support blood cells in lymphatic tissue (nodes, spleen, bone marrow)‏

Blood Vascular tissue Cells with a nonliving matrix (plasma)‏ Fibers = clotting factors Transports nutrients, wastes, gasses, etc.

Muscle Tissue Highly specialized to contract (movement)‏ 3 different types 1. Skeletal 2. Cardiac 3. Smooth

Skeletal Muscle Attached to skeleton Voluntary Pull on bones or skin Long, multinucleated and striated

Cardiac Muscle Only in the heart involuntary Striated, but uninucleated and short/branched cells Held together by intercalated discs (gap junctions)‏

Smooth Muscle Also called visceral muscle Single nucleus, spindle shaped, non-striated Found in the walls of hollow organs Contracts slowly (peristalsis)‏

Nervous Tissue Referred to as Neurons Conducts electrochemical signals Irritability and conductivity Cytoplasm forms long (1m) processes Have supporting cells Makes up the brain, spinal cord, and nerves

Nervous tissue

Tissue Repair Regeneration replaces destroyed or missing tissue Fibrosis replaces the tissue with scar tissue Tissue type Severity of the injury Clean cuts heal better than tears If the gap to fill is smaller then less scarring

General Steps for Repair 1. Capillaries become permeable Clotting factors and immune cells released If exposed to air a scab will form 2. Granulation tissue forms Highly vascular fragile pink tissue Fibroblasts and phagocytes 3. Surface epithelium regenerates Forms just under the scab and covers fibrosis Scab falls off on its own Different tissues heal at different rates!!!!!!!