LECTURE 1
BASIC TISSUES
Classically, the Basic Tissues are: Epithelia, Connective Tissue and the
Excitable Tissues (Nerve and Muscle). This is a core concept of this
course.
EPITHELIAL TISSUES
Objectives
a) To be able to list the Basic Tissues and their general functions
b) To be able to state the general function of lining epithelia.
c) To be able to classify lining epithelia according to morphological criteria.
d) To be able to relate structure and function in lining epithelia
e) To be able to give examples of named epithelia: structure, location, function.
——————
[Epithelium — a single tissue; plural, epithelia; adjective, epithelial]
There are two functional types of epithelium: lining epithelia and glandular epithelium.
Lining Epithelia — cover the free surfaces of the body and its cavities, e.g. epidermis,
lining of the gastrointestinal tract and ducts.
Their position in contact with the environment gives them great importance in
regulating the composition of the body by controlling the movement of materials in
and out.
The structure of lining epithelia can be correlated with their function. Thus the
epithelium of larger ducts is thicker than in smaller ducts; and in sites exposed to
desiccation or friction the epithelium may have a surface coat of keratin, a tough
protein, and is said to be keratinised. (For specific examples of the adaptation of
epithelia to particular function see the organ systems.)
Many epithelia have a high rate of renewal of their constituent cells. For example, the
entire epithelium of the gut is replaced every 6-7 days (equivalent to a daily loss of
1.38 x 109 cells from the small intestine).
1. Structural Characterisation of Epithelia
a) absence of nerves (except for a few axons in the deeper layers)
b) absence of blood vessels — nutrition is by diffusion from the highly
vascular connective tissue (known as the lamina propria) underlying all
epithelia
c) close packing of the constituent cells with minimal intercellular substance
LECTURE 1BASIC TISSUESClassically, the Basic Tissues are: Epithelia, Connective Tissue and theExcitable Tissues (Nerve and Muscle). This is a core concept of thiscourse.EPITHELIAL TISSUESObjectivesa) To be able to list the Basic Tissues and their general functionsb) To be able to state the general function of lining epithelia.c) To be able to classify lining epithelia according to morphological criteria.d) To be able to relate structure and function in lining epitheliae) To be able to give examples of named epithelia: structure, location, function.——————[Epithelium — a single tissue; plural, epithelia; adjective, epithelial]There are two functional types of epithelium: lining epithelia and glandular epithelium.Lining Epithelia — cover the free surfaces of the body and its cavities, e.g. epidermis,lining of the gastrointestinal tract and ducts.Their position in contact with the environment gives them great importance inregulating the composition of the body by controlling the movement of materials inand out.The structure of lining epithelia can be correlated with their function. Thus theepithelium of larger ducts is thicker than in smaller ducts; and in sites exposed todesiccation or friction the epithelium may have a surface coat of keratin, a toughprotein, and is said to be keratinised. (For specific examples of the adaptation ofepithelia to particular function see the organ systems.)Many epithelia have a high rate of renewal of their constituent cells. For example, theentire epithelium of the gut is replaced every 6-7 days (equivalent to a daily loss of1.38 x 109 cells from the small intestine).1. Structural Characterisation of Epitheliaa) absence of nerves (except for a few axons in the deeper layers)b) absence of blood vessels — nutrition is by diffusion from the highlyvascular connective tissue (known as the lamina propria) underlying allepitheliac) close packing of the constituent cells with minimal intercellular substance
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