SfM - Tissues

Question 1

what are the 4 tissues?

Answer 1

nerve, epithelia, connective, muscle

no-one ever compliments me

Question 2

what is the role of epithelial tissue?

Answer 2

• covers surfaces (epithelium), connects cells and separates compartments (endothelium)
• cells define function and have diversity of secondary functions
• involved in gland formation

Question 3

how does epithelial tissue maintain coverage of surfaces?

Answer 3

• 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)

Question 4

what are the classifications of epithelia?

Answer 4

• 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

Question 5

what does connective tissue do?

Answer 5

• connects tissue
• extracellular matrix and fluid defines structure and function
• can vary between liquid to solid matrix

Question 6

how does muscle tissue differ from other cells?

Answer 6

• contractile units of long thin cells (skeletal/cardiac = striated, smooth muscle = non-striated)
• cytoplasm of cells packed with contractile apparatus
• contraction shortens length

Question 7

what is nervous tissue and its components?

Answer 7

• nervous tissue is vital in communication
• receive, generates and transmits electrical signals and integrates information
• neurone is basic component

Question 8

what is a gland?

Answer 8

glands are secretory structures made up of collections of secretory epithelial cells (ileum -> goblet cells -> mucus)

Question 9

what are the two types of glands?

Answer 9

• 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

Question 10

examples of exocrine glands

Answer 10

• simple - either tubular or acinar (grape on a vine)
• compound - tubuloacinar (combination of the two - tends to be branched)
• mucous and serous glands = exocrine

Question 11

production of exocrine secretion

Answer 11

• 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.

Question 12

what do endocrine glands secrete?

Answer 12

proteinaceous secretions

i. e. secretion of proteins
- similar machinery to exocrine glands

Question 13

examples of exocrine glands?

Answer 13

• steroid secretions (lipid soluble - means they can’t be stored in vesicles - store the pre-requisite form instead)
• adrenal cortex, gonads

Question 14

what does the liver do?

Answer 14

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

Question 15

what is the role of epithelium in kidney?

Answer 15

• 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

Question 16

abnormal functions of epithelial cells

Answer 16

• over/under-proliferation
• over/under-secretion
• loss of cilia/ciliary beat

Question 17

abnormal function of glands

Answer 17

• pituitary glands - produces growth hormone (over-production - giantism/under-production - dwarfism)
• uterine tube - mucous glands (over-production - chlamydia - thick mucus -> infertility)

Question 18

what is the ECM composition?

Answer 18

can be fibres, a jelly-like ground substance or liquid fluid

Question 19

what are the fibres made of?

Answer 19

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

Question 20

what is the jelly-like ground substance made of?

Answer 20

made up of proteoglycans or glycoproteins

- these are hydrophilic so absorb water = jelly like consistency

Question 21

what is loose connective tissue?

Answer 21

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)

Question 22

what is dense connective tissue?

Answer 22

• dense regular tissue - contents well arranged and organised for specific functions (tendons)
• dense irregular tissue - sebaceous gland in skin (secretes products)

Question 23

abnormal function of connective tissues

Answer 23

• blood/bone marrow - leukaemia

- bone - osteoporosis