BIPEDALISM AND SKIN

Question 1

What are the 3 types bipedalism

Answer 1

Facultative: temporal basis for particular function

Habitual: on a regular basis

Obligate: when only form of hominin locomotion

Question 2

What are the 2 phases of the human walking gait style

Answer 2

First: Stance phase where the leg is on the ground

Second: Swing phase when leg is off the ground

Question 3

What are some of the advantages of bipedalism

Answer 3

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

Question 4

What is arboreal quadrapedalism

Answer 4

Equal limbs for gait efficiency

Bending of elbows and knees

Diagonal couple gait, one limb moves forward while others grasp a support

Question 5

Explain the locomotion in organutans, gorillas and bonobos/ chimpanzees

Answer 5

Orangutans: brachiation, climbing, arboreal quadrapedalism

Gorillas: Quadrapedal, knuckle walking, occasional bipedalism, can climb

Bonobos and chimpanzees: knuckle walking, sometimes bipedal, climbing/swinging

Question 6

What is a mental eminence

Answer 6

A chin first seen in homo sapiens

Question 7

What are the 4 types of hand positions in quadrupedal motion

Answer 7

Palmigrade (palm grasp)

Digitigrade (digits horizontal)

Knuckle walking

Suspensory (grasping branch

Question 8

What are parts of our anatomy that have evolved due to bipedalism

Answer 8

Vertebral column
Foramen magnum
Pelvis
Gluteal muscles
Femur and tibia
Talus, big toe and longitudinal arch
Limb proportion

Question 9

Explain how the vertebral column evolved due to bipedalism

Answer 9

S shaped spine in stead of C shaped due to secondary curvatures

Increase in vertebra size from cervical to lumbar

wide sacrum

Question 10

Explain how the foramen magnum and nuchal plane evolved due to bipedalism

Answer 10

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

Question 11

Explain how the pelvis evolved due to bipedalism

Answer 11

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

Question 12

Explain how the gluteal muscles evolved due to bipedalism

Answer 12

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)

Question 13

Explain how the femur and tibia evolved due to bipedalism

Answer 13

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

Question 14

Explain how the talus, big toe and longitudinal arch evolved due to bipedalism

Answer 14

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

Question 15

Explain how limb proportion evolved due to bipedalism

Answer 15

Index calculated by dividing length of forelimbs by hindlimb and x 100.

Humans < 100 arms smaller than legs

Baboons = 100

Gibbons > 100 long forelimbs

Question 16

What are the parts of the integumentary system

Answer 16

Skin, hair, nails, sweat/oil/mammary glands

Question 17

What are the functions of the integumentary system

Answer 17

resistance to trauma and infection

barrier to UV light

thermoregulation

sensation

nutrition

Question 18

Outline the specialised cells in the epidermis

Answer 18

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

Question 19

Outline the layers of the epidermis

Answer 19

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.

Question 20

Outline the dermis

Answer 20

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

Question 21

What are the accessory structures of the skin

Answer 21

Hairs
Sebaceous glands
Sweat glands
Nails

Question 22

What are the different parts of a hair

Answer 22

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

Question 23

What are the different types of hairs

Answer 23

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

Question 24

Explain sebaceous glands and nails

Answer 24

Sebaceous glands: secrete sebum which coats hairs

Nails: keratinous structure produced by nail root.

Question 25

Explain sweat glands

Answer 25

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

Question 26

What are the factors skin colour can be influenced by

Answer 26

Carotene: orange-yellow to red pigment body synthesises into vitamin A

Hemoglobin: red pigment when combined with O2

Melanin: explained in another

Question 27

Explain what melanin is

Answer 27

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)

Question 28

What is skin colour intensity due to

Answer 28

Number of melanosomes and dispersion and degradation

Rate of melanin production

degree of melanisation of melanosomes

Rate of transport to keratinocytes

chronological age

Question 29

What are the 2 types of melanin

Answer 29

Eumelanin: Most abundant, high conc in darker skin, produces brown hair

Pheomelanin: High conc in redhead people. Produces blonde hair

Question 30

What happens when melanin dies

Answer 30

Produce grey, wavy hair

Question 31

Explain Gloger’s rule

Answer 31

natural selection favours darker pigmentations where UV radiation is higher (warm/humid habitats)

Question 32

Does Glogers rule relate to reproduction

Answer 32

Possibly as higher UV radiation exposure leads to skin cancer

But, likely already reproduced before onset of skin cancer

Question 33

What is the relationship between darker skin evolution and thermoregulation

Answer 33

As hair was lost due to thermoregulation from the sun, darker skin provided more protection that hair used to

Question 34

What biological processes is vitamin D involved in

Answer 34

Bone metabolism
Innate immune response
Cell proliferation and differentiation

Question 35

What is the relationship between skin colour evolution and vitamin D formation

Answer 35

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

Question 36

What is the folate hypothesis

Answer 36

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