M1, T4: Tissues Flashcards
What are tissues?
- 4th level of organisation
- A group of cells and extracellular matrices¹ that work together to carry out specialised activities
1) Material between the cells, provides structural and functional support to tissue.
Properties of extracellular matrix (EM) affecting tissue
- Hard, dense EM → solid tissue (bone)
- Gel-like EM → semisolid tissue (fat)
- Fluid EM → liquid tissue (blood)
Epethelial (Ep) tissue overview
AKA epithelium
- Cell arrangement: continuous sheets, closely packed together
- Very little EM
- Forms coverings and linings¹
- Forms glands
- Avascular²
1) Membrane that covers another tissue e.g. skin 2) No blood vessels in it
Structure of Ep tissue
- Free surface: exposed, apical layer of cells
- Basement membrane: anchors to underlying tissue at deepest part
- Individual cells:
- ↑ Apical surface: side of Ep cell facing the free surface
- ↓ Basal surface: side of Ep cell facing the basement membrane
- ←→ Lateral surface
Layer classifications of Ep tissue
- Simple Ep tissue: single-layered
-
Stratified Ep tissue: multi-layered
- Apical layer of cells make up free surface
- Basal layer of cells attached to basement membrane
Shape classifications of Ep Tissue
SCC
- Squamous → flat
- Cuboidal → cube-like
- Columnar → column-like
Functions of Ep tissue
- Create selective barriers → intenstinal linings control what foods are absorbed
- Create protective surface → skin
- Secrete substances → sweat glands secrete sweat onto skin
Glandular Ep tissue
- Function is secretion
- Can be isolated
- Can lie in clusters called glands
Define secretion
The release of a substance which benefits the body in some way.
Exocrine glands
External
- Multicellular structures
- Cells of the gland secrete products into ducts
- Ducts carry product to a bodily surface
Endocrine glands
Internal
- Produce and release hormones
- Contain many blood vessels
- Hormones are released into the bloodstream to be distributed throughout the body.
Connective tissue overview
- Cell arrangement: spread out
- Abundant, more developed EM
- Cells involved
- Specialized cells
- Immune cells
- Fat cells
- Cells that create the EM
Extracellular matrix (EM)
In connective tissue
- Composed of ground substance¹ and extracellular protein fibres
- Liquid connective tissues (e.g. blood):
- Lack extracellular protein fibres
- Contain other proteins
1) Ground substance is only in the EM of CONNECTIVE tissue, not in Ep.
Name the 3 types of extracellular protein fibres
In connective tissues
Collagen, elastic and reticular fibres
Collagen fibres
As an extracellular protein fibre
- Strong
- Resist tension
- Flexible
(Think anti-aging products)
Elastic fibres
As an extracellular protein fibre
- Highly elastic
- Stretch and return to original length
Reticular fibres
(‘Net-like’)
- Network of branched proteins
- Provides support to tissue
Ground substance
Including functions
- Filler between cells and fibres
- Can be solid, semi-solid, or liquid
- Functions → supports cells, holds water, facilitates exchange of substances
5 classifications of connective tissue
- Loose connective tissue
- Dense connective tissue
- Liquid connective tissue
- Cartilage
- Bone
What are the specialised cells of muscle tissue known as?
- Muscle fibres (or muscle cells/myocytes)
3 types of muscle tissue and their corresponding muscle fibres
- Skeletal muscle tissue → skeletal muscle fibres (movement)
- Cardiac muscle tissue → cardiac muscle fibres (heart)
- Smooth muscle tissue → smooth muscle fibres (digestion)
Primary property of muscle cells
- Contraction and activation to put force on surrounding tissue
- E.g. Force of skeletal muscle tissue moves the bones of the body, allowing you to move around.
Two types of specialised cells in nervous tissue
- Neurons → transmits electrical signals for communication
- Neurogilial cells → aid neurons in functioning
Cell junctions
Define, state 3 types
- Are the contact points between adjacent plasma membranes of connected cells
- 3 types:
- Gap junctions
- Desmosomes
- Tight junctions
Gap junctions
- Uses channels to freely diffuse substances from one cell to the other
Desmosomes
- Strongly adheres adjacent cells to each other
Tight junctions
- Beads of proteins that wrap around the plasma membranes
- Ensures fluid-tight seal between adjacent cells (no fluid can diffuse into cells)
- Allows fluid to pass in between the adjacent cells’ gap
- E.g. ↓ from free surface to basement membrane
Membranes
- Organ comprised of sheets of Ep and connective tissue
- Flat sheets that create barriers or linings
Mucosa or mucous membranes
(A.K.A. mucous membranes)
- Lines body cavities connected to external environment e.g. oral cavity
- Layers
* Free edge covered in mucous
* Ep tissue
* Underlying connective tissue
Serosa or serous membranes
- Lines body cavities NOT connected to external environment e.g. abdominal cavity
- Lubricates internal bodily surfaces
- Layers (double-layered)
* Thin film of serous fluid between 2 layers
* Ep tissue
* Underlying connective tissue
