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Anatomy II Exam 2: Lectures 9-16 > Lecture 15: Reproductive Specializations > Flashcards

Lecture 15: Reproductive Specializations Flashcards

1
Q

Characteristics of human reproductive system

A
  1. Sexual reproduction (meiosis)
  2. Heterogamy
  3. Amniote
  4. Humans reflect general vertebrate pattern of increased parental investment in offspring
  5. Exhibit live births (viviparity)
  6. Placental mammals
  7. Females exhibit uterus and uterine tubes
  8. Females nourish young with breat milk
  9. Higher primate pattern
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2
Q

What does it mean by heterogamy?

A

In animals it is 2 different cell types (egg and sperm) fusing together

In plants it would be having a male and female part

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3
Q

What does the higher primate pattern include and is it seen in all primates?

A

Not necessarily all primates

Includes development of a simplex uterus and male testes permanently descended into scrotum

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4
Q

What is a simplex uterus?

A

Single unpaired organ, 1 cavity

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5
Q

What type of uterus do anthropoids (monkeys and apes) show?

A

Unicornate

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6
Q

What type of uterus do strepsirhines and tarsiers show?

A

Bicornate

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7
Q

In what ways are humans fairly distinct from other mammals and primates?

A
  1. No baculum
  2. Enlarged external genitalia in both males and females
  3. Heavy menstrual flow
  4. Menopause
  5. Hemochoral placenta
  6. Birth canal constricted as consequence of bipedal adaptations
  7. Fetal head fits tightly through female pelvic outlet
  8. Fetus has characteristic passes through birth canal
  9. Longer labor
  10. Assistance to mother required at delivery?
  11. Relatively altricial infants
  12. Maternal milk higher in carbs, lower in fats and proteins
  13. Permanent relative enlargement of female breasts
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8
Q

Where is the baculum found?

A

Bone found in penis of most placental mammals

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9
Q

Why might humans have lost the baculum?

A

When monogamy became dominant reproductive strategy

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10
Q

What could congential mullerian anommalies lead to?

A

Could lead to fertility problems or endometriosus

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11
Q

Describe the baculum

A

Evolved in mammals 95 mya
Present in first primates
Longer or more prominent bacula appear to be associated with species that characteristically exhibit longer bouts of copulation

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12
Q

Describe secondary sexual characteristics

A

Males and females of a species tend to show observable, distinguishing physical characteristics
Sexual selection may account for many of these traits
Hormones are linked to sexual dimorphism
Additional physiological differences

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13
Q

What are the three different types of placentas?

A

Epitheliochorial
Endotheliochorial
Hemochorial

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14
Q

What species exhibit a epitheliochorial placenta?

A

Cow
Pig
Horse
Strepsirhines (lemurs, lorises, galagos)

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15
Q

What species exhibit an endotheliochorial placenta?

A

Dog

Cat

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16
Q

What species exhibit a hemochorial placenta?

A

Human
Rodent
Haplorhines (tarsiers, monkeys, apes)

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17
Q

What are the secondary sexual characteristics of a female human?

A

Mature breasts
Broader hips
Pubic hair

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18
Q

What are the male human secondary sexual characteristics?

A 
Enlarged Adam's apple
Facial hair
Broad shoulders
Increased body hair
Pubic hair
Mature genital organs
Body more muscular
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19
Q

What is the classic definition of secondary sexual characteristics?

A

Includes only those physical features that arise at puberty and distinguish males and females, but are not necessarily directly involved in reproduction

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20
Q

How does Langdofurther define secondary sexual characteristics?

A

Those characteristics that represent normal responses of various body tissues to the dominant presence of either estrogen or testosterone

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21
Q

What are the female human secondary sexual characteristics under Langdofurther definition?

A
  1. Growth and maturation of sex organs
  2. Breat development
  3. Accelerated ossification at puberty
  4. Increase in subcutaneous fat
  5. Subcutaneous fat depositions associated with breasts and lower body
  6. Softer skin, highly vascularized
  7. Increased Na, H2O retention
  8. Repro. And mothering behaviors
  9. Relative lack of body hair
  10. Increased pheromone sensitivity
  11. Wider hips
  12. Higher pitched voice
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22
Q

What are the male human secondary sexual characteristics as defined by Langdofurther?

A
  1. Sexual differentiation at fetal stage
  2. Descent of testes at 8mos gestation
  3. Growth and maturation of sex organs
  4. Overall body growth
  5. More protein synthesis/muscle development
  6. Ossification of long bones and growth of cortical bone
  7. Increased facial and body hair
  8. Thicker skin
  9. Increase in sebaceous gland activity
  10. Spermatogenesis
  11. Reproductive behaviors
  12. Decreased pheromone sensitivity
  13. Inhibition of GnRH in hypothalamus
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23
Q

Describe the hemochorial placenta

A

Capillaries embedded/efficient
Nutrient transfer
More bleeding

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24
Q

Describe endotheliochorial placenta

A

Capillaries separated by epithelium
Slower nutrient transfer
Less bleeding

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25
Q

What are some examples of secondary sexual characteristics in other species?

A

Differences in body size
Nose size
Mandrills have huge canines and painted face = males
Lions = manes or not

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26
Q

Define reproductive sucess

A

Having as many offspring as possible survive into adulthood

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27
Q

What are the three subclasses of mammals?

A

Prototherians
Metatherians
Eutherians

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28
Q

Describe prototherians reproductive strategy

A

Lay eggs

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29
Q

Describe metatherians reproductive strategy

A

Retain egg in uterus for an entire ovulatory cycle
Fetus then flushed out with endometrial lining
Underdeveloped fetus emerges from birth canal and stays in pouch

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30
Q

Describe eutherians reproductive strategy

A

Endometrium is retained
Placenta supplies developing fetus
Extended gestation
More developed fetus at birth

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31
Q

Most vertebrates (particularly mammals and birds) have relatively __________ offspring in a lifetime and therefore exhibit a relatively ________ degree of parental investment

A

Few

High

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32
Q

Describe the endometrium

A

Highly vascularized
Increases in thickness
Sheds during course of ovulatory (menstrual) cycle
In mammalian uteturs

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33
Q

Within primates, human menstrual flow is __________ and more ________ than that of other species

A

Heavier

Conspicuous

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34
Q

Why is there a greater proliferation of the endometrial lining in mammals?

A

In preparation for sustaining a developing fetus via placental nourishment

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35
Q

Why do primates have a reliance on longer gestation periods?

A

Allow for relatively larger fetal brains may account for differences in endometrial proliferation

36
Q

What do some argue menstruation provides protection against?

A

Invading pathogens

37
Q

Endometrial tissue is an _________ secondary consequence of reproductive cycles

A

Expensive

38
Q

A relatively higher number of ovulatory/menstrual cycles over an individual lifetime has been linked to what?

A

Endometriosis
Anemia
Breast cancer

39
Q

What are the internal genitalia of the male?

A 
Testis
Epididymis
Ductus deferens
Prostate
Seminal glands
Bulborethral gland
40
Q

What are the external genitalia of the male?

A

Penis
Urethra
Scrotum
Coverings of the testis

41
Q

What is the function of the testis?

A

Germ cell and hormone production

42
Q

What is the function of the epididymis?

A

Reservoir for sperm

43
Q

What is the function of the ductus deferens?

A

Transport organ for sperm

44
Q

What are the accessory sex glands in male and what are their function?

A

Prostate, seminal glands, bulbourethral gland

Production of secretions (semen)

45
Q

What is the function of the penis?

A

Copulatory and urinary organ

46
Q

What is the function of the urethra?

A

Conduit for urine and semen

47
Q

What is the function of the scrotum?

A

Protection of testis

48
Q

What are the internal genitalia for females?

A

Ovary
Uterine tube
Uterus
Vagina (upper portion)

49
Q

What are the external genitalia for females?

A 
Vagina (vestibule)
Labia majora and minora
Clitoris
Greater and lesser vestibular glands
Mons pubis
Vulva
50
Q

What is the function of the ovary?

A

Germ cell and hormone production

51
Q

What is the function of the uterine tube?

A

Site of conception and transport organ for zygote

52
Q

What is the function of the uterus?

A

Organ of incubation and partiurition

53
Q

What is the function of the greater and lesser vestibular glands?

A

Production of mucoid secretions

54
Q

What is the function of the mons pubis?

A

Protection of pubic bone

55
Q

What is unique about eutherian mammals?

A

They have a placenta

56
Q

Describe the placenta in mammals

A

Forms an interface between the fetus and mother

Variation among mammals in degree to which placenta invades the uterine lining

57
Q

The difficulty of labor for humans is a trade off for what?

A

Between bipedal adaptations of pelvis and large brain size

58
Q

How does labor for most mammals compare to humans?

A

Appears physically effortless

59
Q

During human birth, what must the infant pass through?

A

Bony pelvis and openings in muscle and fascia that make up the perineum

60
Q

During birth what part experiences the greatest amount of constriction?

A

The infant’s head

61
Q

During birth which part undergoes significant stretching?

A

Soft tissues of perineum

62
Q

During birth what comprises the birth canal?

A

Female pelvis

63
Q

What are the four subtypes of human pelvises?(Caldwell-Moloy Classification)

A

Gynecoid
Android
Platypelloid
Anthropoid

64
Q

Describe the gynecoid pelvis

A

Round pelvic inlet
Shallow pelvic cavity with short ischial spines
Most suitable for childbirth

65
Q

Describe android pelvis

A 
Triangular or heart-shaped inlet 
Narrow anteriorly
Ischial spines are prominent
Tents to be present in taller individuals
Can make childbirth more difficult
66
Q

Describe the platypelloid pelvis

A

Narrow inlet from front to back
Very shallow pelvic cavity
Can make it difficult for the infant’s head to engage the birth canal

67
Q

Describe anthropoid pelvis

A

Inlet is oval and large from front to back and transversely narrow
Larger outlet but relatively small inlet overall
Infant head tends to engage normally, but associated with slower process

68
Q

In most primates, what is the neonatal brain/head size closely correlated to?

A

Maternal pelvis size/shape

69
Q

What is responsible for the human condition of having to pass a very large headed infant through a comparably narrow birth canal?

A

Selection for large brains along with requirement of obligate bipedalism

70
Q

How are squirrel monkeys unique among primate species regarding birth and why?

A

Their infants have relatively large heads at birth

Because they are dwarfed species that reduced in body size over time while maintaining head/brain size

71
Q

What does the known material for Australopithecus afarensis suggest about their birth canal?

A

Wide from side to side, but narrow from front to back

Due to locomotor requirements rather than obstetric constraints

72
Q

What does bipedalism require regarding the evolution of birth?

A

Having sacroiliac (SI) joint as close to acetabulum as possible

73
Q

Describe the evolution of birth and pelvis

A

Wider pelvis to better support hip abductors (small gluteal muscles)

74
Q

Describe the Australopith neonatal brain size

A

Head size is unknown, but this species had a relatively smaller brain size (1/3 modern human) and likely small head

75
Q

Describe the neonatal brain size for Homo erectus

A

Had a relatively larger brain than A. Afarensis
Further adaptations to obligate bipedalism

Similar pelvic dimensions with medium sized head, compared to modern humans would have made for a relatively easy journey through the birth canal

76
Q

Describe the relationship between brain size and gestation in the evolution of birth

A

As brain size increased along with increased adaptations for obligate bipedalism, gestation may have decreased as a compromise to deal with ever increasing brain size

77
Q

What is a defining characteristic of mammals regarding lactation?

A

Early in life, before they can ingest solid foods, young feed on breast milk

Milk comes from breasts of females with exception of certain bats

78
Q

Describe the mammary glands

A

Within breast tissue to produce milk

Specialized exocrine glands derived from sweat

79
Q

How are human breasts unique compared to other primates?

A

In the amount of adipose tissue around the glandular tissue

80
Q

What is excess body fat necessary for regarding birth?

A

Support gestation and feeding of young

Does not explain the presence of excess fat in breast tissue

81
Q

What are some theories about why there is excess fat in female breast?

A
  1. Poorly supported - more attractive to potential males
  2. Fertility advertisements showing good health and plentiful stores of fat, ready for successful reproduction and rearing of offspring
  3. Mature human breasts signal reproductive maturity and potential
  4. “Falsely advertise” and attract males because it was assumed that larger breasts = better milk production (not necessarily true)
82
Q

Where is body size dimorphism common?

A

In mammals, with males typically larger than females

83
Q

What does body size dimorphism tend to relate to?

A

Social structure and associated mating strategies

84
Q

When does sexual size dimorphism tend to be the greatest?

A

When there is a higher degree of male-male competition for females

85
Q

What is lower degree of sexual dimorphism associated with?

A

Polygyny and monogamy where there is little to no male-male competition

86
Q

Has sexual size dimorphism increased or decreased over time in the human lineage?

A

Decreased

Anatomy II Exam 2: Lectures 9-16 (9 decks)

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