M1 Topic 4: Tissues Flashcards
(42 cards)
Tissues
Group of cells (and other things) that work together to carry out specialised activities
- Can be solid (bone), semisolid (fat) or liquid (blood), depending on properties of extracellular matrix
Extracellular matrix
Material between the cells
- Contains substances secreted from cells as well as other materials
- Helps provide structural and functional support to tissue
What are the 4 types of bodily tissues?
- Epithelial tissue
- Connective tissue
- Muscular tissue
- Nervous tissue
Epithelial tissue (epithelium)
Consists of cells arranged in continuous sheets
- Cells closely packed together, little extracellular matrix between cells
- Usually form coverings and linings throughout body (form membrane that covers another type of tissue)
Usually have free surface (uncovered surface)
- E.g. outer layer of skin
Deepest aspect of epithelium is attached to structure called basement membrane
Avascular
What are the 3 main functions of epithelial tissues?
- Create selective barriers that control what enters/exits body (food/drink absorbed into body)
- Secretion of substances (sweat)
- Form protective surface for body
Structure of epithelial tissue
- Apical surface = side that faces free surface of tissue
- Basal surface = faces basement membrane
- Lateral surface = sides of cells
Simple epithelium
Single-layered epithelium
Stratified epithelium
Multi-layered epithelium
Squamous epithelium
Flat cells
Cuboidal epithelium
Shaped like a cube
Columnar epithelium
Shaped like a column
Avascularity of epithelial tissue
No blood vessels
- Blood main transporter of nutrients to bodily tissues
- Common for tissue underlying an epithelium to be rich in blood vessels as nutrients from blood can diffuse up through basement membrane into tissue, can sometimes diffuse through free surface
Two types of epithelial tissue
Covering/lining epithelium
- Covers bodily surface
Glandular epithelium
- Makes gland in body
Main function of glandular epithelium
Secretion
- Lie in clusters called glands
- Classified as exocrine or endocrine glands
Exocrine glands
Multicellular structures arranged into distinct shapes, which all have ducts
- Cells of the gland secret their products into these ducts which carry the substance to a bodily surface
Endocrine glands
Synthesise and secrete type of chemical messenger called hormone
- Have lots of blood vessels that penetrate through them
- Blood vessels carry hormones away from gland and distribute them around body
Connective tissue
Most abundant and widely distributed tissues in the body, has various forms that carry out a variety of functions
Extracellular matrix of connective tissue
Can be hard, soft, liquid, aspect that defines state of connective tissue
Usually made of two major components
- Ground substance
- Extracellular protein fibres (not in liquid connective tissue)
What are the 3 types of extracellular protein fibres?
- Collagen fibres
- Elastic fibres
- Reticular fibres
Collagen fibres
- Very strong, resist tension
- Not stiff, allows tissue flexibility
Elastic fibres
- Highly elastic, stretchable
- Bounces back to original length when force released
Reticular fibres
- ‘Net like’
- Form a network of branched proteins which give tissue a supporting framework
Ground substance
Component of connective tissue between cells and fibres (filler)
- Solid, semi-solid, liquid
- Supports cells
- Holds water (with dissolved solutes)
- Provides medium for exchange of substances between blood and cells
Cells of connective tissues
Generally much more spread out, more abundant extracellular matrix
Types and numbers of cells varies depending on connective tissue, but generally involve…
- Specialised cells that carry out function of tissue
- Immune cells that help fight infection in tissue and repair injury
- Fat cells storing energy substrates that tissue can use to create ATP
- Cells that create extracellular matrix
