journal#1: the human body contains trillions of cells, how many different types do you think there...
TRANSCRIPT
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. 107-118
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