Tissue Types Flashcards
What are the 5 basic tissue types?
1) Epithelial
2) Blood
3) Supporting/ connective tissue
4) Muscle
5) Nervous tissue
What is epithelium?
- Specialised layers of cells in tissues often with a role in separating two spaces
- Epithelial cells are polarised
- Firmly attached to each other and the basement membrane
Describe the basement membrane
- On the basal side of epithelial cells
- Provide support for epithelial cells
- Thin layers of extra cellular matrix
Describe the extracellular matrix
- Between/ beneath cells
- As important as the cells when considering all tissues (especially connective tissues)
- Not single, uniform component
- Not a cell type, rather proteins and polysaccharides
What is the extracellular matrix made of?
What colours do these components stain in H&E?
- Fibres (collagen, elastin) - pink in H&E stain
- Ground substance (polysaccharides) - pale in H&E
Describe the structure of epithelium
- Can be multi-layered or single
- Named according to shape: squamous, cuboidal, columnar
What are the different shapes of epithelium?
- Squamous
- Columnar
- Cuboidal
Name the different layer types of epithelium
Simple
Transitional
Stratified
Pseudostratified
Name 3 examples of epithelium tissues
1) Gut epithelium
2) Epidermis of skin
3) Endothelium
What is haemotology the study of?
Blood
What are the 3 main types of blood cell?
- Leucocytes (white)
- Erythrocytes (red)
- Thrombocytes (platelets)
What is the function of RBC?
Oxygen transport
What is the function of platelets?
Clotting to prevent bleeding
What is the function of WBC?
Defence against infection
What stain do we use for blood smears
Giesma stain
What do RBC look like under a microscope?
- Generally uniform, pink
- Generally smaller in size compared to WBC
- Larger than platelets
- No nucleus in most species
Why do WBC range in staining?
- Differences in cytoplasm
- Differences in cell organelles
- Differences in size
What do platelets look like under the microscope?
- Smaller than RBC or WBC
- Commonly clumped together, diffuse shape
- No nucleus, but cytoplasm is purple stained (due to granules)
Describe a connective tissue
- Not at surface
- Structural and metabolic support for other tissues
- ECM important
- Commonly contain circulatory and lymphatic vessels
Describe the cell of a connective tissue
- Of mesodermal origin
- General role is of the production and maintenance of the |ECM fibroblast and osteocyte)
- Cells make up the majority of the tissue such as adipose tissue
- Can be rarer compared to ECM volume
Describe chondrocytes
- Only present in healthy cartilage
- Produce ECM proteins (collagen, elastins etc.)
- Different ECM composition between differing cartilage types
What are adipocytes?
- Present in a range of supporting tissues
- Adapted for the storage of fat
- Main cell type in adipose tissue
What are the 3 main types of muscle?
Striated
Smooth
Cardiac
Describe skeletal muscle
Specialised in contractions of shorter duration
Relatively strong contractions
Fine control
Voluntary
What does skeletal muscle look like?
- Extremely elongated cells (muscle fibres)
- Multinucleate (a syncytium)
- Striated due to cytoskeleton organisation
- Organised in bundles
Describe smooth muscle
- Specialised in contractions of long duration
- Relatively weak contractions
- Whole region contractions
- Involuntary
- Make up the walls of many organs (e.g., liver, intestines)
What does smooth muscle look like?
- Spindle shaped cells
- No longitudinal arrangement of contractile proteins into myofibrils - no striations
- Central nucleus
What has nervous tissue evolved to do?
Deliver rapid and precise communication between different parts on the body.
What are the two specialised cells in nervous tissue?
Neurons
Glial cells
What are the two subsections of the nervous system?
1) Central nervous system - brain and spinal cord
2) Peripheral nervous system - nerves which run between CNS and other tissues - both contain neurons and glial cells
Describe a neuron in terms of structure
- Vary in shape and size
- Cell body containing a nucleus
- Dendrites which receive a signal
- Cell body that generates action potentials
- Conducts along axon
- Axon ending, signal influences other neurons or effector organ
What are glial cells?
Cells that do not produce electrical signals
- Critical for maintenance and correct function of neurones
- Form myelin for myelin sheath in peripheral and CNS
Which 5 tissues contribute to the cardiovascular system?
1) Blood
2) Muscle (cardiac muscle tissue)
3) Connective tissue (heart valves)
4) Nervous system (sympathetic fibres and parasympathetic fibres)
Describe the myocardium
-Long, cylindrical cells, involuntary contractions
- Striated (parallel stripes)
- Branching
- Behaves as a functional syncytium but cells are discrete
- Divided by specialised intercellular junctions - intercalated disks.
What are intercalated disks?
- They link cells via gap junctions and desmosomes and adherens junctions
- Heart pumps in a wave-like pattern
- They are critical in propagation of action potentials from cardiomyocyte to cardiomyocyte
What are gap junctions in intercalated disks?
Protein tubes called connexons form hydrophilic pores across the plasma membranes of adjacent cells allowing the movement of small solutes
What do desmosomes and adherens junctions both use to link cells?
Cadherins
What do desmosomes do?
Link to intermediate fibres
What do adherens junctions do?
Bind to actin filaments
What does the arterial system do?
Carries blood from the heart to capillaries of the body tissues and organs
What does the venous system do?
Carries blood from the capillary system back to the heart.
What are the 3 layers of blood vessels?
Tunica intima
Tunica media
Tunica adventitia
What is the tunica intima?
- Single layer of flattened epithelial cells called endothelium
- Simple squamous
- Beneath the endothelial cell layer = ECM
- Below ECM = internal elastic lamina (mainly elastin)
- Holes (perforations/fenestrations) within the internal elastic lamina (IEL)
What is the tunica media?
- Mainly muscle layer
- Specifically smooth muscle
- Smooth muscle cells produce ECM and IEL
- Below the muscle cells, the external elastic lamina
What is the tunica adventitia?
- Extracellular matric produced by fibroblasts
- Location of nerves, lymphatic vessels, resident immune cells, progenitor cells.
Describe veins in terms of pressure and connective tissue
Lower pressure
Less smooth muscle and connective tissue
Describe capillaries
- Only the tunica intima layer present
- Allows for movement of cells/ molecules
- Capillary endothelial cells attach to basement membrane
