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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
What are some examples of secondary sexual characteristics in other species?
Differences in body size Nose size Mandrills have huge canines and painted face = males Lions = manes or not
26
Define reproductive sucess
Having as many offspring as possible survive into adulthood
27
What are the three subclasses of mammals?
Prototherians Metatherians Eutherians
28
Describe prototherians reproductive strategy
Lay eggs
29
Describe metatherians reproductive strategy
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
30
Describe eutherians reproductive strategy
Endometrium is retained Placenta supplies developing fetus Extended gestation More developed fetus at birth
31
Most vertebrates (particularly mammals and birds) have relatively __________ offspring in a lifetime and therefore exhibit a relatively ________ degree of parental investment
Few | High
32
Describe the endometrium
Highly vascularized Increases in thickness Sheds during course of ovulatory (menstrual) cycle In mammalian uteturs
33
Within primates, human menstrual flow is __________ and more ________ than that of other species
Heavier | Conspicuous
34
Why is there a greater proliferation of the endometrial lining in mammals?
In preparation for sustaining a developing fetus via placental nourishment
35
Why do primates have a reliance on longer gestation periods?
Allow for relatively larger fetal brains may account for differences in endometrial proliferation
36
What do some argue menstruation provides protection against?
Invading pathogens
37
Endometrial tissue is an _________ secondary consequence of reproductive cycles
Expensive
38
A relatively higher number of ovulatory/menstrual cycles over an individual lifetime has been linked to what?
Endometriosis Anemia Breast cancer
39
What are the internal genitalia of the male?
``` Testis Epididymis Ductus deferens Prostate Seminal glands Bulborethral gland ```
40
What are the external genitalia of the male?
Penis Urethra Scrotum Coverings of the testis
41
What is the function of the testis?
Germ cell and hormone production
42
What is the function of the epididymis?
Reservoir for sperm
43
What is the function of the ductus deferens?
Transport organ for sperm
44
What are the accessory sex glands in male and what are their function?
Prostate, seminal glands, bulbourethral gland Production of secretions (semen)
45
What is the function of the penis?
Copulatory and urinary organ
46
What is the function of the urethra?
Conduit for urine and semen
47
What is the function of the scrotum?
Protection of testis
48
What are the internal genitalia for females?
Ovary Uterine tube Uterus Vagina (upper portion)
49
What are the external genitalia for females?
``` Vagina (vestibule) Labia majora and minora Clitoris Greater and lesser vestibular glands Mons pubis Vulva ```
50
What is the function of the ovary?
Germ cell and hormone production
51
What is the function of the uterine tube?
Site of conception and transport organ for zygote
52
What is the function of the uterus?
Organ of incubation and partiurition
53
What is the function of the greater and lesser vestibular glands?
Production of mucoid secretions
54
What is the function of the mons pubis?
Protection of pubic bone
55
What is unique about eutherian mammals?
They have a placenta
56
Describe the placenta in mammals
Forms an interface between the fetus and mother | Variation among mammals in degree to which placenta invades the uterine lining
57
The difficulty of labor for humans is a trade off for what?
Between bipedal adaptations of pelvis and large brain size
58
How does labor for most mammals compare to humans?
Appears physically effortless
59
During human birth, what must the infant pass through?
Bony pelvis and openings in muscle and fascia that make up the perineum
60
During birth what part experiences the greatest amount of constriction?
The infant's head
61
During birth which part undergoes significant stretching?
Soft tissues of perineum
62
During birth what comprises the birth canal?
Female pelvis
63
What are the four subtypes of human pelvises?(Caldwell-Moloy Classification)
Gynecoid Android Platypelloid Anthropoid
64
Describe the gynecoid pelvis
Round pelvic inlet Shallow pelvic cavity with short ischial spines Most suitable for childbirth
65
Describe android pelvis
``` Triangular or heart-shaped inlet Narrow anteriorly Ischial spines are prominent Tents to be present in taller individuals Can make childbirth more difficult ```
66
Describe the platypelloid pelvis
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
Describe anthropoid pelvis
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
In most primates, what is the neonatal brain/head size closely correlated to?
Maternal pelvis size/shape
69
What is responsible for the human condition of having to pass a very large headed infant through a comparably narrow birth canal?
Selection for large brains along with requirement of obligate bipedalism
70
How are squirrel monkeys unique among primate species regarding birth and why?
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
What does the known material for Australopithecus afarensis suggest about their birth canal?
Wide from side to side, but narrow from front to back Due to locomotor requirements rather than obstetric constraints
72
What does bipedalism require regarding the evolution of birth?
Having sacroiliac (SI) joint as close to acetabulum as possible
73
Describe the evolution of birth and pelvis
Wider pelvis to better support hip abductors (small gluteal muscles)
74
Describe the Australopith neonatal brain size
Head size is unknown, but this species had a relatively smaller brain size (1/3 modern human) and likely small head
75
Describe the neonatal brain size for Homo erectus
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
Describe the relationship between brain size and gestation in the evolution of birth
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
What is a defining characteristic of mammals regarding lactation?
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
Describe the mammary glands
Within breast tissue to produce milk | Specialized exocrine glands derived from sweat
79
How are human breasts unique compared to other primates?
In the amount of adipose tissue around the glandular tissue
80
What is excess body fat necessary for regarding birth?
Support gestation and feeding of young | Does not explain the presence of excess fat in breast tissue
81
What are some theories about why there is excess fat in female breast?
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
Where is body size dimorphism common?
In mammals, with males typically larger than females
83
What does body size dimorphism tend to relate to?
Social structure and associated mating strategies
84
When does sexual size dimorphism tend to be the greatest?
When there is a higher degree of male-male competition for females
85
What is lower degree of sexual dimorphism associated with?
Polygyny and monogamy where there is little to no male-male competition
86
Has sexual size dimorphism increased or decreased over time in the human lineage?
Decreased

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

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