BIPEDALISM AND SKIN Flashcards
What are the 3 types bipedalism
Facultative: temporal basis for particular function
Habitual: on a regular basis
Obligate: when only form of hominin locomotion
What are the 2 phases of the human walking gait style
First: Stance phase where the leg is on the ground
Second: Swing phase when leg is off the ground
What are some of the advantages of bipedalism
Freeing arms to carry objects (like offspring or weapons)
Access to sees and berries in lower branches of trees
Better thermoregulation (less body in sun)
Visual surveillance
Long distance travel
Carrying things on back
What is arboreal quadrapedalism
Equal limbs for gait efficiency
Bending of elbows and knees
Diagonal couple gait, one limb moves forward while others grasp a support
Explain the locomotion in organutans, gorillas and bonobos/ chimpanzees
Orangutans: brachiation, climbing, arboreal quadrapedalism
Gorillas: Quadrapedal, knuckle walking, occasional bipedalism, can climb
Bonobos and chimpanzees: knuckle walking, sometimes bipedal, climbing/swinging
What is a mental eminence
A chin first seen in homo sapiens
What are the 4 types of hand positions in quadrupedal motion
Palmigrade (palm grasp)
Digitigrade (digits horizontal)
Knuckle walking
Suspensory (grasping branch
What are parts of our anatomy that have evolved due to bipedalism
Vertebral column Foramen magnum Pelvis Gluteal muscles Femur and tibia Talus, big toe and longitudinal arch Limb proportion
Explain how the vertebral column evolved due to bipedalism
S shaped spine in stead of C shaped due to secondary curvatures
Increase in vertebra size from cervical to lumbar
wide sacrum
Explain how the foramen magnum and nuchal plane evolved due to bipedalism
Placed more superiorly in modern humans due to perpendicular vertebral column to ground
Nuchal plane (bottom of occipital bone) is parallel to ground in humans
Explain how the pelvis evolved due to bipedalism
Pelvic inlet cannot be too large in human so centre of gravity does not change
Ilium is short and wide and acetabulum is larger to distribute upper body force evenly
Explain how the gluteal muscles evolved due to bipedalism
Larger in primates
Gluteus medius and minimus are placed more at the back of primates and laterally in humans.
This is due to widening and shortening of pelvis and the use of these muscles of abductors not extensors (like in primates)
Explain how the femur and tibia evolved due to bipedalism
Head and condyles are larger and shaft is longer in humans
Bicondylar angle is angled in humans and 90º in a primate.
Articulation with tibia is larger due to human body weight distribution
Explain how the talus, big toe and longitudinal arch evolved due to bipedalism
Talus: parallel articular surface instead of angled more stability in not more motion
Big toe: were divergent in primates for grasping, more for stability now
Longitudinal arch: So blood vessels and nerves are not touching ground, also stabilises
Explain how limb proportion evolved due to bipedalism
Index calculated by dividing length of forelimbs by hindlimb and x 100.
Humans < 100 arms smaller than legs
Baboons = 100
Gibbons > 100 long forelimbs
What are the parts of the integumentary system
Skin, hair, nails, sweat/oil/mammary glands
What are the functions of the integumentary system
resistance to trauma and infection
barrier to UV light
thermoregulation
sensation
nutrition
Outline the specialised cells in the epidermis
Keratinocytes principle cells composed of keratin proteins.
Melanocytes specialised for production of melanin
Merkel cells associated with nerve terminals and sensation
Langerhans cells wondering phagocytic cells of immune response
Outline the layers of the epidermis
1st: stratum corneum and granulosom contain dead and dying cells
2nd: Stratum spinoum containing keratinocytes and langherans cells
3rd: stratum basal includes mitotic stem cells and merkel cells.
Outline the dermis
Strong flexible CT below epidermis. Blood vessels and nerves of skin
Papillary layer contains dermal papillae to increase nutrients and gas exchange
Reticular layer: fibrous tissue
What are the accessory structures of the skin
Hairs
Sebaceous glands
Sweat glands
Nails
What are the different parts of a hair
Bulb: swelling at base in dermis or hypodermis
Root: Epithelial cells produce hair shaft
Shaft: portion above skin surface
Piloerector muscle: erects hair
Inner medulla: soft flexible keratin
Outer cortex: hard keratin
Cuticle: outermost protective layer
What are the different types of hairs
Lanugo: fine, unpigmented, foetus
Vellus: fine, unpigmented, over body
Intermediate: change in distribution (e.g. upper and lower limbs)
Terminal hairs: heavy, pigmented, eyebrows, pubic hair, scalp
Explain sebaceous glands and nails
Sebaceous glands: secrete sebum which coats hairs
Nails: keratinous structure produced by nail root.
Explain sweat glands
In dermis, produce sweat
Apocrine: activated in puberty, large, connected to hair follicle in armpit or pubic area
Merocrine: Small, collected multiples at bottom of sweat pore
What are the factors skin colour can be influenced by
Carotene: orange-yellow to red pigment body synthesises into vitamin A
Hemoglobin: red pigment when combined with O2
Melanin: explained in another
Explain what melanin is
Dark pigment produced by melanocytes of epidermis
no. of melanocytes in everyone is the same
Melanocytes project dendrites into keratinocytes, transfer to mature melanosomes (which contain melanin)
What is skin colour intensity due to
Number of melanosomes and dispersion and degradation
Rate of melanin production
degree of melanisation of melanosomes
Rate of transport to keratinocytes
chronological age
What are the 2 types of melanin
Eumelanin: Most abundant, high conc in darker skin, produces brown hair
Pheomelanin: High conc in redhead people. Produces blonde hair
What happens when melanin dies
Produce grey, wavy hair
Explain Gloger’s rule
natural selection favours darker pigmentations where UV radiation is higher (warm/humid habitats)
Does Glogers rule relate to reproduction
Possibly as higher UV radiation exposure leads to skin cancer
But, likely already reproduced before onset of skin cancer
What is the relationship between darker skin evolution and thermoregulation
As hair was lost due to thermoregulation from the sun, darker skin provided more protection that hair used to
What biological processes is vitamin D involved in
Bone metabolism
Innate immune response
Cell proliferation and differentiation
What is the relationship between skin colour evolution and vitamin D formation
As dark skin blocks sunlight necessary for vitamin D production, northern latitudes evolved depigmented skin to favour synthesis where less sunlight is.
Females have lighter skin maybe due to the need for Vitamin D for high Ca in pregnancy and lactation
What is the folate hypothesis
Adequate folate status is vital for synthesis and repair of DNA.
If exposed to UV radiation undergoes photolysis (light degradation)
Folate deficiency causes developmental degernatuve diseases
Thus, melanin function and darker skin evolved to protect folate from degradation
