Visualizing Changes in Skin Color Due to Pressure. • What is the color of the compressed skin? • What is the reason for the color change? • What would happen if the pressure were continued for an extended time period?
Decubitus Ulcersor Pressure Sores • A decubitus ulcer in an older woman in a nursing home. This was induced because the person was lying in one position for too long, and this compromised blood supply to the skin.
Decubitus ulcers can occur on any point of the body where pressure is being exerted for too long a period of time
Prevention of Decubitis Ulcers • Frequent “rotating” (turning) of bed-bound patients every two hours • Use of soft padding under the patient that reduces pressure to the skin and increases air flow, such as an egg carton pad
3. Making sure the patient’s skin is clean and powdered, to reduce dampness that encourages bacterial growth. 4. Changing sheets immediately if the patient wets the bed.
Viewing Two Types of Pressure Receptors Microscopically • What vegetable did the Paccinian corpuscle remind you of? • What cell does the Meissner corpuscle “touch” in the epidermis? • How does the function of the Paccinian corpuscle pertain to its location?
Determining Two Point Threshold Which area (face, back of hand, palm of hand,, fingertips, lips, back of neck or ventral forearm) has the smallest-point threshold? Why is this?
The human skin contains mechanoreceptors, or receptors that are sensitive to mechanical pressure or deformation of the skin (as in touch) • Concentration of mechanoreceptors within the skin is not uniform. • Highly sensitive areas of skin, such as the lips and fingertips, contain densely packed mechanoreceptors • They monitor the position of our muscles, bones, and joints - the sense of proprioception • Detect sounds and the motion of the body in the inner ear
Insensitive areas, such as the stomach and back, contain lower concentrations of mechanoreceptors. • More sensitive areas of the skin also project to a larger proportion of the somatosensory cortex than less sensitive areas. • Area of the brain which receives touch sensations (for example, from the fingertip) is proportional to the actual sensitivity of the skin area.
Mechanoreceptor Homunculus • Area of the brain which receives touch sensations (for example, from the fingertip) is proportional to the actual sensitivity of the skin area.
Here is a rendering of the sensitivity of areas based on the density of it’s mechanoreceptors. • Ever wonder why your lip feels so fat after anesthesia at the dentists?
Somatosensory Cortex • Located on either side of Fissure of Rolando on the brain • The Fissure itself, when stimulated, causes the motor cortex to be stimulated and the muscles will move
The area of motor cortex controlling a body part is not proportional to the size of that part but is proportional to the number of motor neurons running to it. • The more motor neurons that activate a structure, the more precisely it can be controlled. • Areas of the motor cortex controlling the hands and lips are much larger than those controlling the muscles of the torso and legs. • Therefore, the somatosensory areas will be similar in “size” on the brain!
Dermatomes • Each of the spinal nerves provides sensation to a predictable area of skin. • Pain radiating down the leg to the small toe in the general pattern of the S1 (sacral) dermatome suggests that a herniated disk may be pinching the S1 nerve root in the spine.
Testing Tactile Localization • Does the ability to localize the stimulus improve the second time? The third time? • Explain why. • Which area has the smallest error of localization (and is therefore most sensitive to touch)?
Dyslexia and Tactile Localization • Tactile Localization is used to identify dyslexia by looking at how the brain’s corpus callosum is able to pick up information and transfer it from one side of the brain to another. • If the patient makes three or more errors, his Corpus Callosum is not transferring information from one hemisphere to the other quickly and accurately. • Is indicative of the inability to transfer language from one brain hemisphere to another
Demonstrating the Adaptation of Touch Receptors • What was the duration of sensation on the subjects forearm? • At a different location on the forearm? • Did the pressure sensation return when more coins were stacked on top the original coin? • Are the same receptors being stimulated with four coins as with one coin? Explain.
When pressure is first applied to the corpuscle, it initiates a volley of impulses in its sensory neuron. • However, with continuous pressure, the frequency of action potentials decreases quickly and soon stops. This is the phenomenon of adaptation.
Adaptation occurs in most sense receptors. • Prevents the nervous system from being bombarded with information about insignificant matters like the touch and pressure of our clothing. • Stimuli represent changes in the environment. • No change, the sense receptors soon adapt. • By quickly removing the pressure from an adapted Pacinian corpuscle, a fresh volley of impulses will be generated.
Plotting the Distribution of Sweat Glands Which skin area tested had the most sweat glands?
Did you know… • The density of human sweat glands is determined by the environment you live in • The hotter the environment, the fewer the sweat glands • This is determined by age 3! • Why is this important?
Glands that secrete their products onto body surfaces or into body cavities. Includes mucus sudoriferous eccrine (medocrine) sebaceous ceruminous Exocrine Glands
Sweat Glands Predominately Eccrine Found everywhere except the nipple and parts of external gentalia 2.5 million per person! Are simple, coiled tubes Secrete hypotonic solution that is 99% water, sodium chloride, Vit. C, Antibodies, dermicidin (protein that kills bacteria), urea, ammonia, and lactic acid
Sweat Glands If you drink alcohol you will secrete breakdown products of alcohol, which produces a distinct odor not found anywhere else!
Sweat Glands Mosquitos bite us because we secrete lactic acid! This chemical acts as attractant.
Apocrine Glands Accumulate their products just beneath the surface of the skin Found in axillary and anogenital regions Contain true sweat, plus fatty materials and proteins “Sweat” is odorless, but bacteria on skin decompose it, causing an unpleasant odor
Apocrine Glands Begin functioning at puberty Are influenced by androgens Activated by sympathetic nerve fibers during stress, pain and sexual foreplay
Armpits and Love Current research indicates that the “smell” from the armpit could act as a sexual attractant! Persons who you find unattractive could have some genetic component (from the Major Histocompatability Complex) repellent to you – hence, you are “turned off” by their odor
Ceruminous Glands Secrete ear wax Thought to deter insects, block entry of foreign materials and dampen loud sounds
Ceruminous Glands However, extremely loud music will not be stopped by ear wax. Many musicians, such as Pete Townsend of The Who, are nearly deaf as a result of loud music.
Mammary Glands Secrete a type of sweat that contains protein, lactic acid, water and fats. We call it “milk”.
Holocrine Glands Include the sebaceous glands or oil glands Secrete sebum, which softens and lubricates skin and hair Decrease water loss from skin Is bactericidal (‘bacteria killer’)
Sebaceous Glands Blocked sebaceous glands are at first white. If the sebum oxidizes, the result is a blackhead. Acne is a result of inflamed blackheads, resulting in pus.
“Cradle Cap” • Is a relatively common, oily, scaling, skin condition of the scalp. It also occurs in areas where the skin is normally oily and may spread to the forehead, ears, eyebrows, etc. Occurs from oversecretion of sebum. • In adults it’s called seborrhea.
Function of Hair • Form an insulating coat on the body. Traps a layer of still air just outside the skin, and thereby reduce loss of heat by radiation. • Absorb harmful radiations from the sun. • Keep out coarse dust particles, as in eyelashes, hair in the nasal chambers and ear canals. • Eyebrows prevent water or perspiration from falling into eyes, due to their particular direction.
Axillary and pubic hair lessen friction between limbs and body, and between limbs during locomotion. • Axillary hair provide large surface area for evaporation of sweat by the increase in surface area.
HAIR!!! • Beautify the body • Shaving the head these days is a new phenomenon • Most males are the most decorated organisms in nature, e.g. lion, peacock and other birds, deer, etc.
It’s an Umbrella!!! • Protect from sun and rain. • Prevent water from entering into skin.
Function of nails • Fingernails protect and enhance sensations in your fingertips. • Also help you pick stuff up! • Nails grow through out life; however their rate of growth slows down with age and poor circulation. • Toenails grow slower than fingernails. • Provide something for the toe muscle to push against http://www.indianwomenshealth.com/Know-Your-Nail-139.aspx#
Nail Anatomy • http://www.indianwomenshealth.com/Know-Your-Nail-139.aspx#
Gimme Some Skin Tattooing
History of Tattooing • Goes back to Neolithic tribes • “Otzi” the neolithic man found buried in ice had tattoos • 5,000 year old mummy