Old Skin and Old Muscles: What Happened and Why

These notes provide answers to questions about aging skin and aging muscles.

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1.      Why does skin wrinkle?  
a.       less water in the skin - the skin thins and wrinkles like a grape becoming a raisin
b.   damaged elastin - the skin holds less water and is less elastic, pliable, and resilient  
c.       damaged collagen - the skin holds less water and is less elastic, pliable, and resilient  
less fat - there is less fat under the skin to keep it plump and prevent it from sagging and sinking  

2.      What are age spots (liver spots)?  
a.       uneven distribution of melanocytes and melanin - some areas make more pigment and some areas make less

  3.      Why do bruise marks occur more easily?  
a.       decreased sensation -> increased incident of injuries  
less water in the skin  -> less cushioning  
thinning fat -> less cushioning  
weaker collagen -> easier injury
stiffer elastin -> easier injury  
f.        fewer blood vessel vessels -> weaker skin -> easier injury  
slower healing -> skin stays fragile longer after each small injury, so the damage accumulates  
medications (“blood thinners”) -> slower clotting -> large black and blue marks

4.      What does sunlight do to skin?  
a.       free radicals and cross-linking caused by UV light damage molecules and genes in the skin  
  1.      more irregular keratinocytes (skin cells in the epidermis {outer layer})  
increases in  the uneven distribution of melanocytes and melanin  
reduces Langerhans cells -> more risk of infection and skin cancer plus reduced warning from inflammation  
increases irregularities in elastin  
reduces blood vessels -> less inflammation for warning, reduced regulation of body temperature, reduced vitamin D production and removal  
6.      thicker capillary walls -> reduced supply of nutrients and removal of wastes and Vitamin D for epidermis and the dermis {inner layer of skin})
7.      enlarged sebaceous glands -> adverse cosmetic effects (i.e., blackheads)

5.      What does healthy skin do for the rest of the body and the person?

a.      barrier  
1.      microbes (bacteria and viruses)  
2.      water (keeps body water in while preventing absorption of excess water {e.g., from rain, showers, baths)  
3.      chemical (keeps body substances in while preventing absorption of harmful substances {e.g., soaps, toxins, wastes, pollutants})  
4.      abrasion and trauma (e.g., scraping, rubbing, bumping)  
(a)    epidermis  
(b)   dermis  
(c)    fat tissue  
(d)   hair  
(e)    nails  
5.      light, especially UV light

b.      defense  
1.      Langerhans cells for immune responses against microbes and harmful substances  
2.      WBCs and macrophages against bacteria, viruses, and harmful substances  
3.      vessels and inflammation protect  while promoting healing

c.       information  
1.      for warning  
2.      for enjoyment  

d.      temperature regulation  
1.      fat tissue insulates  
2.      sweat glands cool  
3.      blood vessels regulate the rate of heat loss by enlarging or constricting  

e.      Vitamin D production

f.  cosmetic effects

6.      Why do muscles get weaker and slower?
a.       reduced ability to be stimulated = slower starting and stopping of contraction  
1.      less efficient connections of nerves to muscles plus changes in nerve impulses (weaker, slower, irregular) -> slower starting and stopping of contraction 
b.      storing and generating energy  
1.    reduced storage of energy molecules (ATP, C‑P, and glycogen) plus reduced ability to make energy molecules (e.g., fewer and weaker mitochondria in muscle cells)  
c.       cell thickness  
1.      with less exercise, muscle cells get thinner and weaker
d.      cell number  
1.      loss of muscle cells, unless exercise enlarges and strengthens the remaining cells  
e.      ability to thicken when exercised  
1.      slower increase in muscle size and strength  
f.        proportions of different fiber types  
1.      great decrease in the faster and stronger muscle cells (Type II fibers)  
g.      motor neurons and nerve impulses
1.      fewer nerve cells to stimulate the muscles plus slower and less regular nerve impulses  
h.      muscle mass  
1.      gradual decrease in mass, especially after age 50, and especially with less exercise  
i.        effects =  
1.      less strength  
2.      slower movements  
3.      increased reaction time (longer to start a motion)  
4.      less coordination  
5.      less stamina; i.e., performing extended vigorous activity.  
(a) lowered maximum rate of extended work -> must "pace" slower  
(b)   less endurance for extended hard work -> must "quit" sooner  
(c)    longer recovery time to catch ones breath (e.g., removal of lactic acid)  
(d)   more stiffness and soreness after exercise (from ­ lactic acid build‑up)  
6.      altered posture  
7.      altered appearance and body proportions  
8.      need for fewer calories and diet modification  
9.      need to adjust medications due to altered % body fat vs % lean body mass  
10.  NOTE: great variability among people and among different muscles in a person because of variable decreases in exercise 

7.      Why are complicated motions and new activities more difficult to learn?
a.      motor neurons and action potentials  
1.     less precision of control (from motor neuron "adoption" of abandoned muscle fibers -> increased size of motor units) 
2.      prolonged contractions (from slower and more varied motor neuron impulses)  
3.      effects = reduced speed of starting motion, reduced speed at repetitive motions,  reduced precision of control
b.      brain and spinal cord  
1.      less coordination  
2.      less short term memory -> takes more time to learn a new motion

8.      Why does fatigue develops quicker?
a.       decreased storing and generating energy  
b.      declining cell thickness  
c.       declining cell number  
d.      declining fast and strong muscles cells (Type II fibers)  
e.      fewer motor neurons and irregular nerve impulses
f.        declining efficiency of working (less efficient use of oxygen by the heart, stiffer respiration, stiffer joints), less coordination, altered movement patterns (e.g., walking).
g.       age-related decline in other systems (circulatory, respiratory, integumentary, joint stiffness)  
h.       EFFECTS  
1.      lower maximum rate of extended work -> must "pace" slower  
2.      less endurance for extended hard work -> must "quit" sooner  
3.      longer recovery time to catch one's breath (e.g., removal of lactic acid)  
4.      more stiffness and soreness after exercise (from 8 lactic acid build-up)  
5.     lower VO2 max (maximum rate at which a person can do very vigorous activity {e.g., run})

    (1) effects from ¯ VO2 max

            If VO2max becomes VERY low, even ordinary activities (e.g., going up stairs, carrying household items, walking, getting up from bed or a chair, eating) become difficult

9.      What do healthy muscles do for the rest of the body?  
a.       movement to get what we need and want and to get rid of or escape from what we do not want  
b.      support so other parts can work (e.g., bones, circulation, breathing)  
c.       heat production to stay active rather than becoming dormant or hibernating  
d.      weight control by "burning" calories in food  
e.      use glucose (blood sugars) more effectively to prevent diabetes mellitus  

10.  What do high levels of blood sugar and oxidants from free radicals contribute to aging of skin and muscles?  
1.      damage keratinocytes (free radicals)  
2.      damage melanocytes (free radicals)  
3.      damage Langerhans cells (free radicals and high blood sugar)  
4.      damage sebaceous gland enlargement (free radicals)  
5.      weaken epidermal/dermal boundary leading to easier blistering (free radicals)  
6.      less water content (free radicals)  
7.      slower healing (free radicals and high blood sugar)  
b.      skin and muscle  
1.      damaged collagen fibers (free radicals and high blood sugar)  
2.      damaged elastin fibers (free radicals and high blood sugar)  
3.      damaged  and fewer blood vessels (free radicals and high blood sugar)  
4.      thicker capillary -> less nutrient to the skin cells (free radicals and high blood sugar)  

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    © Copyright 2000 - Augustine G. DiGiovanna - All rights reserved.
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AGING: BIOLOGICAL PERSPECTIVES by Augustine G. DiGiovanna, The McGraw-Hill
Companies, New York, 1994 or 2000; (2) If prior written permission is obtained from Augustine G.
DiGiovanna, Ph.D., Salisbury University  - agdigiovanna@Salisbury.edu