Tissues 1 & 2

Question 1

Describe the basic makeup of tissues.

Answer 1

Tissues are made of cells, extracellular matrix and tissue fluid.

Question 2

Describe the function of connective tissues.

Answer 2

Connective tissues are space filling tissues. They are made of cells and an extracellular matrix. The composition of the extracellular matrix and tissue fluid define the function of the tissue. Connective tissues are identifiable by the fibres present: (collagen + elastin)

Question 3

Describe the function of muscle tissue.

Answer 3

Muscle tissue cells need to be long and thin, so as to contract easily. There is a cytoplasm of cells packed with contractile apparatus.
They shorten lengths, close down spaces.

Question 4

Describe cardiac muscle tissue.

Answer 4

Cardiac muscle tissue is a sort of hybrid of skeletal + smooth muscle tissue, adopting the striations and the less highly ordered arrangement of contractile proteins.
Giving it a stripy appearance.
Cardiac muscle tissue makes up an involuntary muscle, the muscle walls of the heart (which we can’t control).

Question 5

Name some general functions of a nerve cell.

Answer 5

Communication, receives, generate and transmit electrical signal, integrate information.
Generate action potentials and nerve impulses.
Conduction to furthest point of cell.

Question 6

Describe the general histological appearance of a typical nerve cell.

Answer 6

Neurons are stellate, i.e. star shaped. There are 4 regions of neurons, axon, dendrite, axon and cell body (soma).

Question 7

Describe cell - cell junctions; tight junctions.

Answer 7

Tight junctions are also sometimes called occluding junctions as they occlude the space. Their primary function is to seal intercellular spaces and block the movement of material between cells.
(Maintain integrity of epithelial layer - surface covering)

Question 8

Describe cell - cell junctions; gap junctions.

Answer 8

These gap junctions primary function is cell to cell communication and this happens due to a nexus or nexus’.
Gap junctions allow both chemical and electrical signals to pass rapidly from one cell to the next.

Question 9

Describe cell - cell junctions; desmosomes.

Answer 9

Desmosomes or adhering junctions main functions is firm anchorage, this is due to cytoplasmic protein structures called tonofibrils.
(Contribute to the mechanical strength of the tissue, the proteins used resemble the teeth of a zipper keeping or tying the cells together)
Strongest cell-cell junctions.
**desmosomes attach to the intermediate filaments of the cytoskeleton.

Question 10

Describe some secondary roles of epithelial tissues.

Answer 10

Thick epithelium - wear and tear.
Thin epithelium - diffusion.
Movement - due to cilia, finger like projection into lumen from apical surface, there are hundreds per cell. The projections are called villi, you can also get microvilli, this leads to a dramatic increase of the surface area.
Epithelia have good regenerative powers, meaning they are important when skin is torn or cut.

Question 11

Describe the difference between simple and stratified epithelia.

Answer 11

Simple epithelia only have one cell layer, whereas stratified epithelia have two cells or more piled in layers.
In simple epithelia, all cells are in direct contact with the basement membrane. In stratified epithelia, only the bottom layered cells come into contact with the basement membrane (basal lamina)
(Only the basal lamina is capable of reproduction).

Question 12

Name the different cell shapes of epithelia.

Answer 12

Squamous = cells are flat and scale shaped, width is greater than height.
Columnar = height is greater than width, oval shaped nuclei
Cuboidal = cells appear approximately square, sometimes rectangular - identifiable by a circular nuclei.

Question 13

State a specific site in the body where epithelial tissue is found and explain its presence there.

Answer 13

TRANSITIONAL EPITHELIUM - found in urinary bladder, for its protection and impairment.

Question 14

State a specific site in the body in which connective tissue is found and explain its presence there.

Answer 14

Dense irregular connective tissue is found in the fibrous capsule of joints and organs.
+dermis of skin.

Question 15

Describe the functions of epithelial tissue.

Answer 15

Epithelial tissues are continuous sheets of cells that are one or more layers thick.
They cover the exterior surfaces of the body and line internal closed cavities. Make up secretory portions of glands (and their ducts).
Stand on a basement membrane, that is the site of attachment and acts as a filtration barrier. Basement membrane is composed of basal lamina and reticular lamina.
**Any substance that enters or leaves the internal environment of the body must cross an epithelium.

Question 16

State a specific site in the body in which nervous tissue is found and explain its presence there.

Answer 16

The cell bodies of neurons are in the central nervous system (brain and spinal cord) or the ganglia (just outside the spinal cord).
Generate and transmit action potentials and nerve impulses.

Question 17

Compare skeletal and smooth muscle tissues.

Answer 17

Under the microscope, skeletal muscle tissues have a stripy appearance due to them being striated. Skeletal muscle tissues contain many microfibrils.
Smooth muscle tissues are NOT striated and there is NO stripy appearance. They are randomly arranged.
NOTE: the embryonic precursors of skeletal muscle cells are called myoblasts, myo = muscle.

Question 18

Explain the naming process of “pseudostratified columnar epithelium”.

Answer 18

When viewed under the microscope, it looks as though some cells are not in contact with the basement membrane and that the nuclei are at different heights. Appears to be more than one layer of cells.
However, the extracellular matrix shows that all cells are in contact with the basal lamina and so it is actually “simple”.
Some pseudostratified columnar epithelia contain GOBLET CELLS.

Question 19

Describe “goblet cells”.

Answer 19

Goblet cells secrete mucus at the apical surface (refers to the uppermost layer of cells). This mucus is a mixture of glycoproteins and proteoglycins.
The mucus acts as a lubricant for food to be swallowed, as a trap for foreign particles and microorganisms inhaled or ingested and as a protective barrier between the epithelium and the environment.

Question 20

Describe transitional epithelium.

Answer 20

This is a special form of epithelium, in which the cells can alter their shape. When the epithelium is relaxed they appear cuboidal but when stretched they appear squamous.
In unstretched cells, the rounded superficial cells bulge out.

Question 21

Describe the connective tissue; adipose tissue.

Answer 21

These appear rounded and empty looking, as the nucleus is displaced by the fat to the edge of the cell.
These tissues are made of adipocytes; which are fat-storing cells, thought to have been derived from fibroblastic-like cells.

Question 22

Describe loose connective tissue.

Answer 22

Loose connective tissues are the elastic tissues that underlie skin and provide support for small glands.
Loose connective tissue contains many cells, including permanent fixed cells, such as macrophages, mast cells, fibroblasts and adipocytes.
Loose arrangement of fibres (collagen, elastin).
Moderately viscous fluid matrix.

Question 23

Describe the connective tissue; dense irregular tissue.

Answer 23

Provide strength and flexibility
Dense woven network of collagen (and some elastin) fibres in a viscous matrix.
This tissue is impact resistant.
The fibres are all facing in different directions.
Contains fibroblasts.
Forms the debris of the skin.

Question 24

Describe the connective tissue; dense regular tissue.

Answer 24

Collagen fibres are densely packed and arranged in parallel.
Found in ligaments and tendons as they are strong or “powerfully resistant”.

Question 25

State a specific site in the body where muscle tissue is found and explain its presence there.

Answer 25

Cardiac muscle tissue forms the muscular walls of the heart, work to keep blood pumping through the circulatory system.

Question 26

Define the term “glands”

Answer 26

Glands are (mostly) collections of secretory epithelial cells. They can be single or multicellular.
Exocrine (secrete into tube)
Endocrine (secrete into blood)

Question 27

Describe the structure of the ducts of exocrine glands.

Answer 27

The ducts of exocrine glands can be simple (single unbranched duct - glands of large intestine) or compound (branched duct - salivary glands.
They release their secretions to the body’s EXternal environment.

Question 28

Describe the shape of the secretory units of exocrine glands.

Answer 28

Tubular, (like a tube?)
Acinar (grape-shaped)
As a compound = tubuloacinar.

Question 29

Name the 3 methods of exocrine secretion.

Answer 29

Merocrine - product released by exocytosis (most common form of secretion) e.g. most sweat glands.
Holocrine - Whole cell ruptures during release of product, followed by the new cell forming as a result of mitosis and cytokinesis. e.g. sebaceous glands.
Apocrine - portion of cell is pinched off along with the product.

Question 30

Describe mucous secretion.

Answer 30

Secretion is rich in proteoglycans and glycoproteins, not watery but viscid.
The secretion + water = mucus.
E.g. mucous glands of trachea and gut.

Question 31

Describe serous secretion.

Answer 31

Watery secretion that often contains enzymes.
Protein rich.
E.g. exocrine pancreas.
Tears, sweat and digestive enzyme solutions are all serous exocrine secretions.

Question 32

Describe endocrine glands.

Answer 32

Endocrine glands are ductless.
The produce a proteinaceous secretion straight into the blood, which then distributes it to other parts of the body, where the secretions regulate or coordinate the activities of various tissues, organs and organ systems.
E.g. Pancreatic islets.

Question 33

Describe the matrix of connective tissue and its function.

Answer 33

The extracellular matrix of connective tissues is a grounds substance made up of rope-like fibres in a protein and polysaccharidal matrix.
Variations in the composition of the extracellular matrix determines its properties (e.g. if matrix is calcified = bone and teeth)
The ground substance consistency is highly variable (this is how blood is watery, and bone is hardened - yet both are still connective tissue)
The matrix is made of glycoproteins, fibrous proteins and GAGs (glycosaminoglycans)
- All of the above have been secreted by fibroblasts.
GAGs absorb water and this is why the matrix is 90% water (its major component).
GAGs are good at resisting compressions.

Question 34

Define the term ‘glycosaminoglycans’.

Answer 34

Glycosaminoglycans or GAGs are long, linear polysaccharides.
Their function depends on their core protein.
NOTE: All GAGs except hyaluronic acid attach to a core protein.
They are negatively charged.
They are inflexible are cannot fold us like proteins so remain extended and strongly hydrophilic.

Question 35

Describe proteoglycans.

Answer 35

Proteoglycans are GAGs that covalently bond to a core protein. These GAG-protein mixtures are very heterogeneous, and this variability means they can form pores of different sizes to regulate the sizes of molecules that can move through the matrix.

Question 36

Name and briefly describe the fibres within connective tissue.

Answer 36

Collagen - most common fibrous tissue, flexible but inelastic.
Elastin - coiled, wavy protein that returns to its original length after being stretched.
Fibronectin - non-collagenous, fibrous protein that helps cells stick to the extracellular matrix (via focal adhesions). Also play an important role in wound healing and blood clotting.

Question 37

Describe collagen (within connective tissue).

Answer 37

Collagen is important for resisting tensile forces.
Stains with eosin in H&E stains as PINK.
Collagen molecules are often cross-linked.
***Reticular fibres are very fine collagen fibres.

Question 38

Describe the secretion of collagen.

Answer 38

Secreted by fibroblasts as procollagen.
Amino acid residues at ends of procollagen protein are cleaved off outside the cell to form collagen, which then aggregates into fibres.
This prevents formation of large fibres within the cell, which would be harmful.

Question 39

Describe the secretion of elastin.

Answer 39

Elastin’s soluble precursor, tropoelastin secreted from cell, elastin fibres are assembled close to extracellular surface on a scaffold of microfibrils.

Question 39

Describe elastin.

Answer 39

The fibrous tissue, elastin makes tissues elastic and allows them to recoil after stretch.
Mixing collagen and elastin prevents overstretch.
Pale staining because elastin is an amorphous protein.

Question 39

Name and briefly descibe the main cellular components of connective tissue.

Answer 39

Fibroblasts - secrete the non-rigid extracellular matrix
Adipocytes - fat storing cells
Macrophages - phagocytes i.e. engulf bacteria and other particles
Mast cells - key role in allergic reaction, contain large secretory granules of proteoglycan and histamine.
Plasma cells - found in lymph nodes, derived from WBC, important in developing immunity
Myoepithelial cells - (smooth muscle cells) lie between epithelial cells and the basement membrane of ducts. Found in regions of connective tissue where there are glands.

Question 40

Describe the consequences of abnormal function of connective tissue.

Answer 40

In;
Blood/bone marrow = leukaemia.
Loose/dense = loss of or abnormal fibres.
Cartilage = tear
Bone - osteoporosis/petrosis

Question 41

Describe the consequences of abnormal function of epithelial tissue.

Answer 41

Over/ under proliferation
Over/ under secretion
Loss of cilia / ciliary beat.

Question 42

Define a “sebaceous gland”

Answer 42

Sebaceous glands are exocrine glands that secrete a lipid mixture.

Question 43

Define “hemidesmososmes”

Answer 43

Hemidesmosomes tie epidermal cells to fibres of the basal lamina
Hemidesmosomes are strong junctions that anchor intermediate fibres of the cytoskeleton to fibrous matrix proteins.