Week 5 - The Integumentary System

Question 1

What is the tissue type of the epidermis?

Answer 1

Stratified squamous epithelia

Question 2

What is the tissue type of the dermis?

Answer 2

Dense irregular connective tissue

Question 3

List the 4 different cell types found in the skin and their functions

Answer 3

• Keratinocytes - Produce keratin which protects the cells from the external environment
• Melanocytes - produce melanin which protects the skin agaisnt UV radiation
• Langerhans cells - Are dendritic cells which phagocyte foreign substances.
• Merkel cells - sensory receptors for fine touch

Question 4

What layer of the epidermis are the 4 different cell types found in?

Answer 4

• Keratinocytes - All layers
• Melanocytes - stratum basale
• Langerhan cells -All layers (mainly spinosum)
• Merkel cells - stratum basale

Question 5

What are the layers of the epidermis?

Answer 5

• Stratum corneum
• Stratum lucideum
• Stratum granulosum
• Stratum spinosum
• Stratum basale

Question 6

What are the two layers of the dermis and what type of connective tissue are they made from?

Answer 6

• Papillary layer - areolar loose CT

* Reticular layer - dense irregular CT

Question 7

Where are hair follicles found and not found?

Answer 7

Hair follicles are located all over the body except for the lips, palms of hands and soles of the feet.

Question 8

How is hair structurally different from the epidermis?

Answer 8

The keratin in hair cells is tougher and more durable.

Question 9

What are the functions of hair?

Answer 9

• Increase sensation
• Helps prevent heat loss
• Protects the skin for UV radiation

Question 10

How is hair colour determined?

Answer 10

By the amount and type of melanin produced in the outer layer of the hair shaft.

Question 11

How are goosebumps formed?

Answer 11

Erector pili muscles contract causes the hair to stand up

Question 12

Where are sweat glands found on the body?

Answer 12

All over the body except for the nipples and parts of the genitalia.

Question 13

What makes up sweat?

Answer 13

Water, salts and wastes (urea)

Question 14

What is the function of sweat?

Answer 14

Evaporation of sweat has a cooling effect on the body.

Question 15

Where are sebaceous glands found?

Answer 15

All over the body except for the palms of the hand and soles of the feet.

Question 16

What is sebum and what is its function.

Answer 16

Is an oily lubricant that waterproofs the skin and hair and helps protect against microbial growth.

Question 17

What stimulates sebaceous glands and when is their stimulation most active?

Answer 17

Hormones - puberty

Question 18

List and describe the three types of protection that the skin offer

Answer 18

• Physical barrier
• Keratanised layer of dead skin cells protects against
infection
• Chemical barrier
• Skin secretion - sebum creates a low pH
environment that inhibits bacterial growth
• Biological barrier
• Langerhan cells - phagocyose and destroy foreign particles

Question 19

How does the skin regulate body temperature when we get HOT?

Answer 19

• Vasodilation of blood vessels close to the skins surface

* Sweat glands secrete sweat onto the skin which evaporates to help dissipate body heat

Question 20

How does the skin regulate body temperature when we get COLD?

Answer 20

• Vasocontriction of blood vessels close to the skin surface to redirect blood flow to the bodies core.
• arrector pilli contracts causing the hairs to stand on end and trap warm hair close to the skin

Question 21

What are the different sensory receptors found in the skin and briefly list their function

Answer 21

• Meissners corpuscles - fine touch
• Pacinian corpuscles - deep touch
• Bare nerve endings - pain and temperature

Question 22

How is vitamin D produces and what is its function?

Answer 22

It is produced by modified cholesterol molecules located in the epidermal cells - involved in calcium metabolism

Question 23

What kind of wastes are eliminated by the body via sweat?

Answer 23

Nitrogenous wastes (ammonia, urea and uric acid) are eliminated from the body via sweat.

Question 24

What are the four key characteristics of skeletal muscle?

Answer 24

• Excitable - ability to respond to stimuli
• Extensible - ability to lengthen
• Contractible - ability to shorten
• Elastic - recoil back to a passive length

Question 25

``` Identify the following structures of a skeletal muscle: • I band • H zone • A band • Z disk • M line ```

Answer 25

[Google Images]

Question 26

What is the functional unit of a skeletal muscles? why?

Answer 26

Sarcomere - they are the smallest contractile unit

Question 27

Describe the organisation and basic function of myosin, actin, tropomyosin and tropinin.

Answer 27

* Myosin makes up the thick filament - containing myosin heads that bind to actin to produce contraction * Actin - Makes up the thin filament and contains myosin binding sites. * Tropomyosin - located on the thin filaments and blocks mysosin binding sites * Troponin - bound to tropomyosin and free mysoin binding sites when it is bound to calcium

Question 28

Briefly describe the 4 steps involved in the cross bridge cycle

Answer 28

1) Cross bridge formation -calcium ions released from SR bind troponin which allows myosin head to bind actin to form a cross bridge. 2) Power stroke - ADP is released and the mysoin head pivots to slide the actin towards centre of sarcomere 3) Cross bridge detachment - Binding of ATP causes myosin head to detach from actin 4) Reactivation of myosin head - ATP is hydrolysed which activates the myosin head so the cycle can repeat NOTE: Cycle ends when calcium is actively transported back into the SR

Question 29

Briefly describe the six steps involved in the transmission of ADH across the NMJ

Answer 29

1) Action potential arrives at the axon terminal of the motor neuron 2) Voltage gated Ca2+ channels open which cause influx of Ca2+ 3) Ca2+ causes the exocytosis of acetylcholine (ACh) 4) ACh binds to receptors located on the sarcolemma 5) Binding of ACh to ion channels results in the influx of Na+ into the muscles fibres which depolarises the membrane 6) effect of ACh is terminated by diffusion, degradation and re-uptake

Question 30

Explain excitation - contraction coupling

Answer 30

1) Binding of ACh to ligand gated Na+ channels creates an action potential which is propagated along T-tubles to the Sarcoplasmic reticulum 2) SR releases calcium 3) calcium binds to troponin which removes the blocking effect of tropomyosin and uncovers the myosin head binding sites on the actin filament.

Question 31

What are the 3 stages involved in skeletal muscle contraction?

Answer 31

1) Membrane excitation 2) Excitation - contraction coupling 3) Sliding filament mechanism

Question 32

What is the function of intercalated in cardiac muscle?

Answer 32

They bond cardiac cells and help synchronize the contraction of the heart

Question 33

What junctions are present in intercalated discs?

Answer 33

* Gap juctions - allow for the movement of ions to transmit current across the heart * Desmosomes - to keep cardiac cells from separating during contraction

Question 34

What does the term autorhythmicity mean?

Answer 34

Is the ability to spontaneously depolarise without external neural input.

Question 35

Instead of troponin, smooth muscles contain________?

Answer 35

Calmodulin

Question 36

List and describe the three phases of cardiac muscle contraction

Answer 36

1) Depolarisation - Voltage gated Na+ channels in the sarcolemma open allowing the influx of extracellular sodium 2) Plateau - Depolarisation is transmitted down the T-tubules to the sarcoplasmic reticulum (SR) which causes it to release Ca2+ - also opens Ca channels in the sarcolemma. 3) Repolarisation - Is due to Ca2+ channels closing and K+ channels opening which brings membrane potential back to resting.

Question 37

Why is the 2nd stage of cardiac contraction called the plateau phase?

Answer 37

Because the release of calcium from the sarcoplasmic reticulum prolongs depolarisation.

Question 38

What type of channel become inactivated in the repolarisation phase of cardiac muscle contraction? What type of channel opens?

Answer 38

Ca2+ inactivated | K+ open