SfM - Tissues Flashcards
what are the 4 tissues?
nerve, epithelia, connective, muscle
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what is the role of epithelial tissue?
- covers surfaces (epithelium), connects cells and separates compartments (endothelium)
- cells define function and have diversity of secondary functions
- involved in gland formation
how does epithelial tissue maintain coverage of surfaces?
- cell-cell junctions (desmosomes/tight junctions maintain integrity
of epithelial layer)(gap junctions involved in cell-cell communication) - cell-ECM junctions (hemidesmosomes found in epidermis of skin linking cell and ECM)
what are the classifications of epithelia?
- simple - single layer of epithelia (squamous - long squished cells/cuboidal - square shaped/columnar - rectangular cells)
- stratified - multiple layers of epithelial cells, can be of any type
- transitional - multiple layers of mixed cell types
- pseudostratified - single layer of cells, however gives appearance of multiple layers due to organisation
what does connective tissue do?
- connects tissue
- extracellular matrix and fluid defines structure and function
- can vary between liquid to solid matrix
how does muscle tissue differ from other cells?
- contractile units of long thin cells (skeletal/cardiac = striated, smooth muscle = non-striated)
- cytoplasm of cells packed with contractile apparatus
- contraction shortens length
what is nervous tissue and its components?
- nervous tissue is vital in communication
- receive, generates and transmits electrical signals and integrates information
- neurone is basic component
what is a gland?
glands are secretory structures made up of collections of secretory epithelial cells (ileum -> goblet cells -> mucus)
what are the two types of glands?
- endocrine (secretes into blood) - cells lose contact with surface & surround blood vessel, means product can be secreted directly into blood
- exocrine (secretes into tubes) - cells stay in contact with surface via a tube like space
examples of exocrine glands
- simple - either tubular or acinar (grape on a vine)
- compound - tubuloacinar (combination of the two - tends to be branched)
- mucous and serous glands = exocrine
production of exocrine secretion
- there is a polarisation of the cell.
- The basal part of the cell predominantly deals with the production of the secreted substance.
- The middle section contains lots of vesicles, ready to package the product.
- The apical part of the cell deals with the physical secretion of the product via membrane.
what do endocrine glands secrete?
proteinaceous secretions
i. e. secretion of proteins
- similar machinery to exocrine glands
examples of exocrine glands?
- steroid secretions (lipid soluble - means they can’t be stored in vesicles - store the pre-requisite form instead)
- adrenal cortex, gonads
what does the liver do?
epithelial components of the liver are parenchyma (hepatocytes)
- hepatocytes arranged in rows between BVs, focussed around the bile ducts
- involved in secretion, support epithelial cells
what is the role of epithelium in kidney?
- kidney has cortex (coat), medulla (drains into pelvis), pelvis (drains into ureter), ureter (passes into bladder)
- epithelial cells organised into nephrons - involved in filtration of blood, absorption, release urine from kidney, line BVs, line renal pelvis
abnormal functions of epithelial cells
- over/under-proliferation
- over/under-secretion
- loss of cilia/ciliary beat
abnormal function of glands
- pituitary glands - produces growth hormone (over-production - giantism/under-production - dwarfism)
- uterine tube - mucous glands (over-production - chlamydia - thick mucus -> infertility)
what is the ECM composition?
can be fibres, a jelly-like ground substance or liquid fluid
what are the fibres made of?
collagen
- provides great tensile strength
- 19+ types (1 - tendons, 3 - reticulin/lymph, 4 - basal lamina)
- collagen produced by fibroblasts (release pro-collagen, protein creates triple stranded helix = collagen fibril, these accumulate to form collagen fibres (100x thicker))
- also made from elastin which allows stretch - found in sheets rather than fibres
what is the jelly-like ground substance made of?
made up of proteoglycans or glycoproteins
- these are hydrophilic so absorb water = jelly like consistency
what is loose connective tissue?
loose accumulation of cells/widely spread
- permanently fixed cells = fibroblasts, macrophages, adipocytes, mast cells
- transient cells = white blood cells (only in v.loose connective tissue)
what is dense connective tissue?
- dense regular tissue - contents well arranged and organised for specific functions (tendons)
- dense irregular tissue - sebaceous gland in skin (secretes products)
abnormal function of connective tissues
- blood/bone marrow - leukaemia
- bone - osteoporosis
