Tissues are groups of cells with a common structure (form) and function (job). There are four main tissues in the body – epithelium, muscle, connective tissue and nervous tissue.
I. EPITHELIUM (EPITHELIAL TISSUE)
1) Closely attached to each other forming a protective barrier.
2) Always has one free (apical) surface open to outside the body or inside (cavity) an internal organ.
3) Always had one fixed (basal) section attached to underlying connective tissue.
4) Has no blood vessels but can soak up nutrients from blood vessels in connective tissue underneath.
5) Can have lots of nerves in it (innervated).
6) Very good at regenerating (fixing itself). i.e. sunburn, skinned knee.
1) By shape:
a) squamous - flat and scale-like
b) cuboidal - as tall as they are wide
c) columnar - tall, column-shaped
2) By cell arrangement:
a) simple epithelium - single layer of cells (usually for absorption and filtration)
b) stratified epithelium - stacked up cell layers (protection from abrasion - mouth, skin.)
There is also pseudostratified epithelium - looks like stacked cell layers, but is actually a single layer of cells (trachea and upper respiratory tract, it secretes muscous and its cilia helps to propel foreign material out of the body through coughing)
II. CONNECTIVE TISSUE
The 3 Elements of Connective Tissue:
1) Ground substance – gel around cells and fibers
2) Fibers – provide strength, elasticity and support
IIa. SPECIAL CONNECTIVE TISSUES
More about Bone Tissue and Bone Structure: LINK
III. NERVOUS TISSUE
Conducts impulses to and from body organs via neurons.
The 3 Elements of Nervous Tissue:
2) Spinal cord
More about how nervous tissue works: LINK
IV. MUSCLE TISSUE
The 3 Types of Muscle Tissue:
More about how muscular tissue works: LINK
Body Tissues (Histology) Color Mini-Poster: LINK
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Amsel, Sheri. "Tissues - Epithelium, Muscle, Connective Tissue and Nervous Tissue (Histology)" Exploring Nature Educational Resource ©2005-2021. January 19, 2021
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