Journal#1: The human body contains trillions of cells, how many different types do you think there are? Fun Fact: The human heart creates enough pressure to squirt blood 30 feet in the air. Objective: – List the 4 major tissue types in the body –Discuss the types and functions of epithelial cells

Epithelial Tissue Pgs

Intro to Tissues Combinations of specialized cells that work together to perform a function The study is called Histology Four Basic Tissue Types –Epithelial –Connective –Muscle –Neural

Epithelial Tissue Includes : –Epithelia: Layers of cells that cover internal & external surfaces –Glands: Structures that make fluid secretions and are attached to or derived from the epithelia Characteristics –Cellularity: cells bound by cell junctions –Polarity: has an exposed & attached surface –Attachment: the base is bound to a thin basal lamina with connective tissue below –Avascularity: no blood vessels –Regeneration: Replaced by stem cells in the epithelium (high mitotic rate)

Functions of Epithelial Tissue Protection: from abrasion, dehydration, and destruction Control permeability: create a semi permeable barrier Provide Sensation: sensory receptors (skin) Produce Secretions: gland cells produce enzymatic fluids, hormones, etc.

Specialization Move fluids over surface Move fluids through the epithelium Produce Secretions Specialized Structures –Microvilli (increase surface area for absorption and secretions) –Ciliated epithelium (beat cilia to move fluids across cell)

Intercellular Connections Epithelial Cells firmly attached to each other Also attached to basal lamina –Where stem cells or germinative cells are located Adjacent cells connected by proteins called cell adhesion molecules (CAMs) Types of cell junctions (connections) –Tight: lipid portion of membrane joined by interlocking proteins (adhesion belt) Prevent diffusion between cells –Gap: held together by interlocking proteins Allows diffusion between cells –Desmosome: attach cells to extracellular structures like the basal lamina

Journal#2: What are the 3 types of cell junctions or connections in epithelial tissue? Fun Fact: Feet have 500,000 sweat glands and can produce more than a pint of sweat a day. Objective: – List the 4 major tissue types in the body –Discuss the types and functions of epithelial cells

Classification of Epithelium Cell shape: –Squamous: thin and flat –Cuboidal: little boxes –Columnar: tall and slender Layers: –Simple: 1 –Stratified: more than one

Squamous Simple –Delicate –Diffusion ready –Blood vessels, tubules of kidneys, lining of cornea, mesothelium (lining of body cavities) Stratified –Protection –Skin, lining of mouth, throat, esophagus

Cuboidal Simple –Limited protection –Absorption/Secretion –Kidney Tubules, Glands, Ducts Stratified (rare) –Protection –Absorption/Secretion –Ducts of sweat glands

Transitional Tolerates stretching without damage Urinary bladder –Empty: seems to be layered w/cuboidal on surface –Full: appears flattened like simple squamous

Columnar Simple –Absorption/secretion –Lining of stomach & intestines Pseudostratified ciliated –Protection/secretion –Nasal cavity, trachea, & bronchi Stratified (rare) –Protection –Pharynx, epiglottis, anus, & urethra

Glandular Endocrine Glands –Release fluids (hormones) into interstitial fluid –Directly to bloodstream Exocrine Glands –Release fluids on to epithelial surface –Skin/sweat, tears in eyes, milk by mammary glands

Modes of Secretion Merocrine –Exocytosis of secretory vesicle –Perspiration, mucus Apocrine –Loss of cytoplasm becomes secretion –Milk production Holocrine –Lysis releases secretory products –Sebaceous glands (hair follicles)

Types of Secretions Serous glands –Watery solution (saliva) Mucous glands –mucous Mixed Exocrine glands –both

Gland Structure Unicellular (goblet cells) Multicellular –Secretory sheet –Simple: single duct –Compound: duct divides many times