Tissues Flashcards
Define the term ‘epithelium’ and describe the basic functions of epithelial surfaces, those covering the body and lining internal structures.
Epithelial tissue covers surfaces and separates compartments.
It has no contact inhibition, and forms cell-cell and cell-ECM junctions to fill any gaps.
Also has secondary functions, determined by its thickness (thin = diffusion, thick = protection) and presence of cilia (movement) and microvilli (absorption).
Describe the types of surface epithelia and explain how the structural properties of each correlates with its functions.
Simple
o Squamous e.g. Alveoli and Capillaries. Thin to allow for easy diffusion.
o Cuboidal e.g. Lining of nephrons. Perform secretion and absorption/pumping.
o Columnar e.g. Lining digestive tract. When ciliated, move mucus
Stratified
o Squamous e.g. Epidermis. Thick, and layers can be sloughed off to allow new growth.
o Cuboidal e.g. ducts of sweat glands. Protection.
o Columnar e.g. Pharynx. Protection and secretion.
Describe the epithelial components of the liver and kidney.
Liver
o Hepatocytes
o Arranged in rows (or cords) between blood vessels
o Multiple functions including secretion.
o Support epithelial cells line blood vessels and bile ducts.
Kidneys
o Epithelial cells
o Arranged into nephrons
o Multiple functions including filtration of blood, partial absorption of filtrate
o Support cells line blood vessels and renal pelvis which receives toxic urine.
Consider the consequences of abnormal function of covering and lining epithelia.
o Over/Under proliferation - cancer
o Over/Under Secretion
o Loss of ciliary beat
Define the term ‘gland’ and describe the basic functions of glandular epithelium.
Glands are collections of multi or single cellular secretory epithelial cells.
- Endocrine: Secretes into blood e.g. Adrenal Cortex
- Exocrine: Secretes to surface e.g. Sweat glands
Can also be simple or compound glands, which can have linear or acinar structures.
Acinar ducts usually used for secretion, as it would be difficult to expel the substances in the long tubular ducts
Consider the consequences of abnormal glandular function.
Over production – Pituitary giantism
Under production – Pituitary dwarfism
GSH abnormal production
Define the term ‘connective tissue’ and describe its basic functions.
Connective tissue - tissue that connects, supports, binds, or separates other tissues or organs, typically having relatively few cells embedded in an amorphous matrix, often with collagen or other fibres, and including cartilaginous, fatty, and elastic tissues.
Includes fibres (collagen and elastic), ground substance, tissue fluid and loose connective tissue (e.g. fixed and transient cells)
Describe the matrix, fibre and cellular components of connective tissue and explain the function of each.
Fibres
• Collagen - Makes up 30% body weight. Flexible, but inelastic with great tensile strength. 19+ types?
• Elastic Fibres - Protein Elastin. Stretch 1.5x length and return to original shape. Microfibrils and amorphous component. Found in sheets. Yellow colour.
Ground Substance
• Proteoglycans (Protein core and GAGS)
• Hyaluronic Acid
• Glycoproteins
Tissue Fluid
Loose Connective Tissue
• Fixed cells – Fibroblasts, Macrophages, Adipocytes, Mast cells
• Transient cells – White Blood Cells
Consider the consequences of abnormal function of connective tissues.
- Blood / bone marrow - leukaemia
- Loose / dense - loss/abnormal fibres
- Cartilage - tear
- Bone – osteoporosis
- Epidermolysis bullosa (EB) is a group of inherited connective tissue diseases that cause blisters in the skin and mucosal membranes. It is a result of a defect in anchoring between the epidermis and dermis, resulting in friction and skin fragility.
Describe muscle tissue types and function
- Has the ability to contract and produce force and movement, often connected to bone, excitable
- Three types of muscle tissue: cardiac, smooth muscle (internal organs) and skeletal muscle
- Long thin cells
- Cytoplasm of cells packed with contractile apparatus
Describe neural tissues and its function
- For communication – can carry information in the form of chemical and electrical signals from one part of the body to another
- Made up of two types of cells: Neurons + support cells (glial cells)
- Receives, generates and transmits electrical signals
- Integrates information
- Concentrated in the brain and spinal cord but also include a network of cells that extend to virtually every part of the body
Compare and contrast collagen and elastic fibres
Collagen • 30% body weight • Inelastic but flexible • Great tensile strength • 19 types (+), made by fibroblasts • Type I in tendons • Type III is reticulin • Type IV in basal lamina (non-fibrous)
Elastic fibres
- Protein elastin
- Stretch 1.5 times
- Microfibrils and amorphous component
- Generally in sheets rather than fibres
- Yellow colour (aorta)
Describe different types of dense connective tissue
- Dense regular –made up of parallel collagen to form tense structures e.g. tendons and ligaments
- Dense irregular – made up of randomly aligned collagen e.g. muscle, nerve sheaths, sebaceous glands
Describe the development of exocrine and endocrine glands
- During development, epithelial cells grow downward into their supporting connective tissue.
- In the development of exocrine glands, they remain connected to the parent epithelium, and a hollow center, or lumen, forms to create a duct that provides a passageway for secretions to move to the surface of the epithelium and into the external environment.
- In endocrine glands, they lose the connecting bridge of the cells that links them to the parent epithelium. Their secretions then go directly into the bloodstream.
How does epithelial tissue maintain coverage of surfaces?
No contact inhibition
Cell-cell junctions
Cell-ECM junctions
