Types of Epithelium and Tissues (PDF)

# Types of Epithelium ## Simple Squamous Epithelium - **Function:** Allows simple diffusion of gases, nutrients, and waste across a thin membrane - **Location:** Air sacs of lungs, capillary walls, interior of heart (endothelium), lining ventral body cavities (mesothelium) ## Simple & Stratified...

# Types of Epithelium ## Simple Squamous Epithelium - **Function:** Allows simple diffusion of gases, nutrients, and waste across a thin membrane - **Location:** Air sacs of lungs, capillary walls, interior of heart (endothelium), lining ventral body cavities (mesothelium) ## Simple & Stratified Cuboidal Epithelia ### Simple - **Function:** Secretion, absorption, and protection (glandular cells) - **Location:** Kidney tubules, secretory portions of the thyroid, salivary glands ### Stratified - **Function:** Duct lining; secretion, absorption, and protection - **Location:** Sweat glands, mammary glands ## Simple Columnar Epithelium - **Function:** Secretion of enzymes, mucous or other substances; absorption - **Location:** Digestive tract - **Goblet cells:** A type of columnar cell that is a unicellular, mucous-secreting gland found in digestive and respiratory tracts ## Transitional Epithelium - **Function:** Allows for distension without tearing the membrane - **Structure:** Modified stratified epithelium (cells change shape from round to flat) - **Location:** Urinary bladder ## Pseudostratified Columnar Epithelium - **Function:** Protection, secretion, movement of mucous - **Location:** Nasal cavity, trachea, bronchi, parts of male reproductive tract # Glands: One or more cells that make and secrete a product ## Endocrine - Blood is shown being transported in capillaries - Hormones are secreted into the blood ## Exocrine - Chemical secretions are secreted by the gland to the skin surface # Apocrine Secretion - **Ap- = separating from** - **Loss of cytoplasm along with the secretion through packed vesicles in the apical portion of the cytoplasm.** - **Example:** Milk production # Merocrine/Eccrine Secretion - **Most common mode of secretion** - **Secretion released from secretory vesicles by exocytosis** - **Examples:** - Mucous that traps bacteria - Lubricates and protects lumens - Sweat that cools the body # Holocrine Secretion - **Gland cell bursts when cell is packed with secretion.** - **Example:** Sebaceous glands - oil glands attached to hair follicles all over the body # Skeletal Muscle - **Nucleus Number:** Multiple - **Striated:** Yes - **Voluntary/Involuntary:** Voluntary - **Cell Division:** No - **Function:** Provides body heat. Protein fibers contract, shortening the muscles which pull on bones or skin causing movement # Smooth Muscle/Visceral Muscle - **Nucleus Number:** Single - **Striated:** No - **Voluntary/Involuntary:** Involuntary - **Cell Division:** Yes - **Function:** Propels or squeezes substances through hollow organs by alternating between contracting and relaxing. Makes up walls of vessels # Cardiac Muscle/Myocardium - **Nucleus Number:** Single - **Striated:** Yes - **Voluntary/Involuntary:** Involuntary - **Cell Division:** No - **Function:** Gap junctions between intercalated discs help muscle cells to synchronize contractions # Function of Skin - **Protection:** From external environment - **Excretion:** Salts, water, wastes - **Maintains internal temperature:** Insulation/sweating - **Melanin production:** Protects from UV rays - **Water resistant:** Keratin protects against water loss - **Vitamin D synthesis:** Assists calcium metabolism - **Sensation:** Touch, pain, pressure, temp # Layers of Skin - **Stratum Corneum:** Dead cells flaking off at the skin surface - **Stratum Lucidum:** Only in thick skin: palms & soles - **Stratum Granulosum:** - **Stratum Spinosum:** - **Stratum Basale:** Keratinocytes move up as they age # Melanin: Pros and Cons ## Pros 1. Protects DNA from ultraviolet rays (natural sunblock) ## Cons 1. Melanin blocks UV rays, which are needed for vitamin D production: risk of not enough vitamin D # Sebaceous Glands - **Structure:** Holocrine gland that have ducts opening into hair follicles - **Function:** Secretes sebum: a lipid substance (oil): softens & lubricates hair/skin, bactericidal - **Location:** All over body except for palms/soles feet # Sweat Glands: Apocrine - **Structure:** Ducts empty into hair follicles - **Function:** Active at puberty, most active in stress/emotional situations - **Location:** Underarms, genitals, around nipples - **Secretion:** Same as sweat with additional fatty acids & proteins, Milky white/yellow; slight odor: produces unpleasant musky order when decomposed by bacteria # Sweat Glands: Merocrine/Eccrine - **Structure:** Single coiled tube in dermis: duct of tube opens to sweat pore - **Function:** Thermoregulation, response to stress, lowers pH and acts as antibiotic - **Location:** All over body: forehead, upper lip, palms, soles - **Secretion:** Sweat (water, salts, wastes & vitamins), pH 4-6 - Dermcidin: antibiotic in sweat to protect against bacterial growth # Ceruminous Glands - **Function:** Protects ear drum, keeps outer ear drum surface pliable, waterproofed, blocks entry of foreign material - **Location:** Dermis of ear canal - **Secretion:** Cerumen (earwax)