Tissues IA %%? (+ Flashcards
4 Types of tissues
- Epithelia
- Connective
- Muscle
- Nervous
Epithelial tissue
- Covers surfaces
- Separates compartments
- Cells define function
- Forms glands
Connective tissue
- Connects!
- Extracellular matrix + fluid defines structure and function
- Liquid to solid matrix
Muscle tissue
- Contractile (Can contract)
- Long thin cells
- Cytoplasm of cells packed with contractile apparatus
- Shorten lengths, close down spaces
- 3 types: Skeletal, smooth, cardiac muscle
Muscle tissue histology
Skeletal
- Striated
– highly ordered arrangement of contractile proteins
Cardiac
- Striated
– highly ordered arrangement of contractile proteins
Smooth
Non-Striated (smooth)
– less ordered arrangement of contractile proteins
Nervous tissue
- Communication
- Neurons + supporting cells
- Receives, generates and transmits electrical signals
- Integrates information
Basic components of nervous tissue
Plasma membrane electrical signals
–generation (nerve impulses/action potentials)
–conduction to farthest points of cell.
Neurons - 4 regions:
- cell body (soma),
- dendrites,
- axon
- terminals.
How does epithelial tissue maintain coverage of surfaces?
- No contact inhibition
- Cell - cell junctions
- Cell - ECM junctions
Cell-cell junctions: Desmosomes
- Intercellular junctions that provide strong adhesion between cells.
Cell – cell junctions: tight junctions
- aka occluding junctions
- seals intercellular spaces
- Maintain integrity of epithelial layer (surface covering)
Cell – cell junctions: gap junctions
- aka communicating junctions; nexus
- Function: cell-to-cell communication
Basement membrane
- The basement membrane is a thin, fibrous, extracellular matrix of tissue that separates the lining of an internal or external body surface from underlying connective tissue in metazoans.
- This surface may be epithelium (skin, respiratory tract, gastrointestinal tract, etc.) or endothelium (blood vessels, lymph vessels, etc.)
Cell – ECM junctions pic
Cell-Extracellular matrix
Epithelium secondary roles
- When thick – wear and tear
- When thin - diffusion
- Movement (Cilia): Finger like projection from apical surface (side facing lumen)
- Absorption (Microvilli): Finger like projection from apical surface
Epithelial classification 1 (3 types)
1) squamous: thin and flat
2) cuboidal: small cubes in cross section
3) columnar: tiny columns
Epithelial classification 2: Layering
1) simple: one layer of cells
2) stratified: cells arranged in two or more layers
3) pseudostratified: falsely appear to be layered
Glands
- Collections of secretory epithelial cells (mostly)
- Single celled or multicellular
- Exocrine (secrete into tubes), and
- Endocrine (secrete into blood).
Development of exocrine and endocrine glands
Exocrine glands
Difference between exo and endocrine glands
- Exocrine secretes chemical through ducts to external
- Endocrine (ductless glands) secretes chemicals directly into blood
Examples of exocrine glands
Mucous glands
- Secretion rich in proteoglycans
- Secretion + water gives mucus
- Eg. Mucous glands of trachea , gut.
Serous glands (secrete enzyme solutions. e,g serous cells of the salivary glands)
- Protein rich secretion
- Eg. Exocrine pancreas
Endocrine glands
Proteinaceous secretion such as hormones.
Epithelial components of liver
Parenchyma – Hepatocytes (epithelial cells)
- Hepatocytes arranged in rows (or cords) between blood vessels
- Multiple functions, including secretion
Epithelial components of kidney - 1
Epithelial components of kidney - 2
Parenchyma (the functional tissue of an organ as distinguished from the connective and supporting tissue.) – Epithelial cells
- Epithelial cells organised into nephrons
- Multiple functions, including filtration of blood, partial absorption of filtrate, overall to release urine from kidney
Abnormal function of epithelial cells
- Over-proliferation
- Under-proliferation
- Over-secretion
- Under-secretion
- Loss of cilia / ciliary beat
Abnormal function of glands - 1
Pituitary gland
- Over production of growth hormone – pituitary giantism
- Under production of growth hormone – pituitary dwarfism
Abnormal function of glands - 2
Uterine tube
- Mucous glands (single cell glands)
- Chlamydia trachomatis (STD)
- Thick mucus can lead to Ovum/sperm trapped – infertility
Connective Tissue
- Blood / bone marrow
- Mucous
- Reticular
- Loose
- Dense - regular
- Dense - irregular
- Cartilage
- Bone
- Adipose (fat)
Connective tissue
Extracellular matrix (ECM)
- Fibres – ‘rope-like’
- Ground substance – ‘jelly-like’
- Tissue fluid - liquid
Connective tissue - ECM
Fibres
- Collagen–( type 3 reticulin)
- Elastin
Collagen
- 30% body weight
- Inelastic but flexible
- Great tensile strength
- 19+ types
- Type I in tendons
- Type III is reticulin
- Type IV in basal lamina (non-fibrous)
Elastic fibres
- Protein elastin
- Microfibrils and amorphous (without a clearly defined shape or form) component
- Generally found in sheets rather than fibres
- Yellow in colour (aorta)
Ground substance - semi-solid gel
- Proteoglycans (protein core + glycosaminoglycans)
- Hyaluronic acid
- Glycoproteins (laminin, fibronectin, )
- Tissue fluid
Loose connective tissue
Permanent (fixed) cells
- Fibroblasts
- Macrophages
- Adipocytes
- Mast cells
- Undifferentiated mesenchyme cells
Dense Connective tissue
Abnormal function of Connective Tissue
- Blood / bone marrow - leukaemia
- Loose / dense - loss/abnormal fibres - (epidermolysis bullosa- diseases that cause blisters in the skin and mucosal membranes)
- Cartilage - tear
- Bone – osteoporosis/petrosis
