Chapter 2: Cells and Tissues
Lesson 2.3

Tissues are groups of cells with similar structure that join together to perform a common function
- the study of tissues is Histology
- tissues are classified into four main types;
1. Epithelial – lines and cover
2. Connective - supports
3. Muscle – generates force
4. Nerve – conveys information
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I.
Epithelial Tissue
- Epithelia – tissues that cover the body and line body cavities
- Gland – tissues that secrete chemicals
endocrine gland tissue – secrete to other parts inside the body
exocrine gland tissue – secrete to outside world
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Four main functions of Epithelial Cells:
1. protect body from physical damage
2. control what enters and leaves the body
3. provide sensory input
4. secrete various substances
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- Apical surface – faces the outside world or lumen of a body cavity connected to outside world
- Basal surface – faces deeper body cells
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Epithelia: Cell Layers and Shapes
- Epithelia are classified by:
1. layers
Simple = one layer
Stratified = multiple layers
2. shape
Squamous = almost flat
Cuboidal = height equal to width
Columnar = tall and skinny
IF multiple layers not same shape = classified as shape of the most apical cells
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• simple
– one layer
• stratified
– more than one layer
• other
– transitional
• stretchable
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Simple Epithelia
- Simple Squamous = single layer of flattened cells, allow for rapid diffusion (thin)
+ gas-exchanging cavities = alveoli in lungs
+ lining of abdominal cavity
+ endothelium, single layer, lining blood vessels/heart
- Simple Cuboidal = single layer typically involved in secretion or absorption
+ surround tubules in kidneys and secretory glands
- Simple Columnar = single layer, secretory or absorptive
+ linings of ducts in kidneys, stomach and intestine
+ may contain microvilli to increase surface area
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Stratified Epithelia
- Stratified Squamous – where mechanical and chemical protection is most needed
+ skin – outside surfaces (apical) are dead and dying cells along with protein keratin.
Provides a waterproof barrier to combat dehydration.
+ other apical surfaces include; mouth, throat, esophagus, anus, rectum
- Stratified Cuboidal = (rare) duct of sweat gland
- Stratified Columnar = (rare) duct linings of pancreas and salivary glands
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Transitional epithelia does not fit the other classifications
Example:
Bladder
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Glands – epithelial cells that secrete a substance(s)
1. Exocrine gland – secretes products to outside world a. unicellular exocrine glands – isolated cells in lining of respiratory and digestive tracts they secrete mucus to form protective cover over epithelium
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b. multicellular exocrine glands – two parts, secretory cells that make product and duct cells that connect gland cells to surface of epithelium c. simple duct structure = single or compound – can be tubular or alveolar (spherical)
2. Endocrine gland secrete to interstitial space (spaces between tissues)
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True or False?
1. Connective tissue provides support.
2. Transitional epithelial stretches.
3. Cuboidal cells are flat.
4. Stratified means more than one layer.
5. Epithelial glands secrete substances.
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• functions
– strengthens the body and organs
– protects internal organs
– maintains the shape of organs
– provides rigid framework for muscles to pull
• fibers
– collagen
– reticular
– elastic
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• connective tissue proper
– wide variety of locations and functions
– plays a role in immune defenses
• cartilage
– provides support and flexibility
– minimizes friction
• bone tissue (osseous tissue)
– provides framework, protects organs, supports body
• blood
– provides transportation, regulation, and protection
– carries oxygen and nutrients, and carbon dioxide
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• connective tissue proper
– loose
– dense
• cartilage
• bone
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• loose connective tissue
– areolar – under epithelium
– reticular – spleen
– adipose – fat
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• dense connective tissue
– regular dense–tendons
– irregular dense–dermis
– dense elastic–large artery walls
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• chondroblasts
• hyaline
– ends of long bones
• elastic
– external ear
• fibrocartilage
– intervertebral discs
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• osseous tissue
– protects organs
– supports the body
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• skeletal
• cardiac
• smooth
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• central nervous system
• peripheral nervous system
• glial cells
• neurons
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Match the following with 1 –4 below: skeletal, collagen, nervous tissue, elastic cartilage.
1. muscle tissue type
2. external ear
3. fiber
4. glial cells
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