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