FHMP 021 + 022 Epithelium and skin and its histology

Question 1

What are the 5 primary tissues?

Answer 1

• connective tissue
• epithelial tissue
• muscle tissue
• nervous tissue
• blood tissue

Question 2

what are the common feature of epithelial tissue?

Answer 2

• closely packed cells with little extracellular material
• cells linked together via anchoring junctions (attachment and watertight seal)
• below epithelial tissue is always basal lamina and connective tissue
• has apical and basal surfaces
• renews rapidly
• can undergo metaplasia (can differentiate into a different cell type)
• cells have polarity
• has extra functions such as diffusion barrier, secretion, absorption, protection

Question 3

what is the basal lamina?

Answer 3

• part of the basement membrane

- connects the epithelia to the connective tissue underneath

Question 4

what are the 4 ways to classify epithelia?

Answer 4

1. number of cell layers ( simple, stratified)
2. shape of cell (squamous, cuboidal, columnar)
3. specialised features ( cilia, microvilli, keratin)
4. apical (dead) or middle (differentiating) or basal (stem cell)

Question 5

what is apical and basal?

Answer 5

• apical = surface facing the lumen/top

- basal = surface facing basal lamina/ connective tissue/ bottom

Question 6

what is simple squamous epithelium and where is it found?

Answer 6

• 1 layer of flat epithelial cells

- endothelium of blood vessels, heart, lungs and loop of Henle

Question 7

what is simple cuboidal epithelium and where is it found?

Answer 7

• 1 layer of cuboidal epithelial cells

- small ducts for secretion or absorption

Question 8

what is simple columnar epithelium and where is it found?

Answer 8

• 1 layer of columnar cells

- stomach, intestines, for absorption

Question 9

what is stratified squamous epithelium and where is it found?

Answer 9

• many layers of flat epithelial cells

- skin (keratinised) oesophagus, vagina, anus, for protection

Question 10

what is stratified cuboidal epithelium and where is it found?

Answer 10

• many layers of cuboidal epithelial cells

- large ducts, e.g. mammary gland, salivary gland, sweat gland

Question 11

what is stratified columnar epithelium and where is it found?

Answer 11

• many layers of columnar epithelial cells

- rare large ducts e.g. conjuctiva

Question 12

what is pseudo-stratified epithelium and where is it found?

Answer 12

• it is a single layer of epithelial cells but the cells are all of different lengths (some don’t reach the surface) and the nuclei appear at different layers, so it looks stratified
• usually ciliated, respiratory epithelium of trachea and bronchi

Question 13

what is transitional epithelium and where is it found?

Answer 13

• where the surface epithelial cells change depending on a state
• the cells are usually stratified cuboidal but the surface cells (umbrella/capping cells) change shape due to stretching or relaxing and change to stratified squamous)
• urinary epithelium (bladder)

Question 14

what are the different junctions/ connectors between cells (5)?

Answer 14

• tight junction
• adherens junction
• desmosome
• gap junction
• hemidesmosome

Question 15

what do gap junctions do?

Answer 15

• allow transport of water, ions and other substances between cells
• important in heart for ion transport for electrical signalling

Question 16

what do tight junctions do?

Answer 16

• create a watertight seal between cells
• create impermeable barrier
• e.g. in bladder prevent urine from leaking out into extracellular space

Question 17

what do desmosomes do?

Answer 17

• adhere / join adjacent cells together to ensure that cells in tissues that stretch like skin or muscle remain connected in an unbroken sheet

Question 18

what do hemidesmosomes? do?

Answer 18

• connect basal surface of epithelial cells to the basal lamina

Question 19

what do adherens junctions do?

Answer 19

• join cells together (adhere)
• can create a marginal band around a cell connecting it to other cells
• this band can contract (contains actin) which can deform the shape of the cells, e.g. form a duct

Question 20

what are the 5 functions of epithelia?

Answer 20

1. protection ( physical - keratin -, UV radiation - melanin -, immunity)
2. excretion (sweat glands)
3. chemical synthesis (vit D)
4. thermoregulation (sweat glands and hair follicles)
5. sensation (nerve endings)
   (SPECT)

Question 21

Give some structures found within epithelia / epidermis / dermis / hypodermis

Answer 21

• dermis ridges (ridge where epidermis extends to the dermis to increase anchoring)
• keratinocyte
• melanocyte
• sebaceous gland
• Langerhans cells (type of macrophage)
• nerves
• hair follicles
• blood vessels
• erector pili muscle (hair)
• collagen and elastin fibers
• fat/adipose tissue

Question 22

what is the epidermis, dermis and hypodermis?

Answer 22

• epidermis = topmost layer, contains epithelium
• dermis = middle layer, contains connective tissue, nerves, blood vessels, hair follicles, glands
• hypodermis = bottom layer, mostly contains fat/adipose tissue and blood vessels

Question 23

what do red blood cells look like under the microscope?

Answer 23

• red/pink colour
• no nucleus
• round/disc shape
• usually within vessesl

Question 24

what are the 3 layers of blood vessels?

Answer 24

1. intima (innermost, endothelium, thin layer of squamous epithelial cells)
2. media (middle, smooth muscle layer)
3. adventitia ( connective tissue and elastic fibres)