TISSUES
• Tissues - cells working
together to perform a
common function
• Histology - Study of tissues
4 BASIC TYPES
• Epithelial - covers & lines surfaces, forms
glands
• Connective - connects tissues, provides
support, stores energy reserves
• Muscle - Contracts for movement, generates
heat
• Neural - Carries information from one part of
body to another in the form of electrical
impulses
Epithelial Tissue - layer of cells
that forms a barrier
• Functions:
– provides physical protection
– controls permeability
– provides sensations
– produces secretions
• Characteristics:
– consists mainly of cells
– consists of single layer or multiple layers
– always has a free surface exposed to the environment
– avascular
– mitotic rate can be very high
Intercellular Connections
• Tight Junction - formed by fusion of cell
membranes
• Desmosome - thin proteoglycan layer
between opposing cell membranes
• Gap Junction - binding of membrane
proteins
CLASSIFICATION
Subdivided according to shape & arrangement of
cells in each type
• Arrangements:
• Shapes:
• Squamous - flat
• Cuboidal - cubed
• Columnar - higher than
wide
• Simple - single layer of
same shape
• Stratified - many layers of
same shape
• Transitional - several layers
of differing shapes
http://trc.ucdavis.edu/biosci10v/bis10v/media/ch20/epithelial_structure.html
Bell work Questions
Aug 20th
1.
2.
3.
4.
5.
6.
What are the four types of tissues?
Define tissue.
The study of tissues is call ______________.
How are Epithelial tissues named?
What are the 3 basic shapes of epithelial tissues?
What are the 3 basic arrangements of epithelial tissues
SIMPLE SQUAMOUS
(most delicate)
• Locations
– Alveoli in lungs
– blood & lymphatic
vessels
• Functions
– Reduce friction
– Diffusion of gases
– Controls permeability
STRATIFIED SQUAMOUS
(tough)
• Locations
– Surface of skin
– Lining of mouth,
throat, esophagus,
rectum, vagina
• Functions
– Protection against
abrasion, pathogens,
and chemicals
SIMPLE CUBOIDAL
• Locations – glands, ducts, kidney
tubules, thyroid gland
• Functions – protection, secretion,
and/or absorption
STRATIFIED CUBOIDAL
(RARE)
• Locations – lining of some ducts
like sweat glands
– Mammary glands
• Functions – Protection, secretion,
absorption
TRANSITIONAL EPITHELIUM
(STRETCHY)
• Locations – Urinary bladder,
ureters
• Functions – Permits expansion &
recoil after stretching
SIMPLE COLUMNAR
• Locations– Lining of stomach,
intestine, gallbladder,
uterine tubes,
collecting ducts of
kidneys
• Functions – Protection, secretion,
absorption
PSEUDOSTRATIFIED
COLUMNAR EPITHELIUM
• Locations -
– lining of nasal cavity,
bronchi, trachea
• Functions – protection, secretion
– Nuclei are located at
varying distances from
surface
STRATIFIED COLUMNAR
Relatively Rare
• Locations – pharynx,
epiglottis,
anus,
mammary
ducts,
urethra
• Functions – Protection
Bell work
Glandular epithelium
•
Cells that make up glands are specialized to produce and
secrete substances
Types of secretions from cells
•
–
–
1. endocrine
•
•
Glands that secrete their products into tissues or blood
Ex: Pituitary and sex glands
2.
exocrine
a.
Merocrine: release products by exocytosis
Ex: salivary glands/ pancreas
b.
a.
Apocrine: Lose small portions of glandular bodies during secretion
ex: mammary glands: fat droplets/sweat glands
Holocrine: entire cell disintegrates
Ex: sebaceous glands of skin (fatty mixture called sebum)
Reflection
• How are epithelial tissues classified?
• How can you i.d. if a tissue is an epithelial?