Ch. 11 - Reproduction [Dr. Wood Mammalogy]

Monotremes

Cloaca, only the left ovary is functional

Marsupials

Cloaca, simple placenta• Brief gestation, long nursing period

Altricial

Useless baby for marsupials and Monotremes

Placentals

highly efficient placenta. Respiratory, circulatory, and excretory systems integrated w/mother. Longer gestation, shorter nursing period

Gestation

The process or period of developing inside the uterus between conception and birth. 10-14 days in dasyurids to 650 days in elephants

Lactation

The process of producing and releasing milk from the mammary glands in female mammals, including humans, from 4 days in hooded seals to 900 days in chimps

Intervals

3-4 weeks between litters in rodents to 3-4 years in whales, elephants, rhinos

Testes

produce sperm/testosterone, contained in the scrotum

Position varies

bats/rodents - descend from the abdominal cavity during breeding season, then withdraw

Armadillos: always in the abdominal cavity

Primates, carnivores, and ungulates remain descended

Spermatogenesis

The process by which male germ cells in the testes produce mature sperm cells, or spermatozoa

Seminiferous tubules

sperm production

Sertoli cells

"nurse" cells; provide nutrients

Leydig cells

secretes testosterone

Glands

seminal vesicles, prostate, and bulbourethral. secretions to enhance the alkaline level of semen = increased survival in the acidic environment of the urethra/vagina

Coagulating glands

The copulation plug blocks the vagina. Retain sperm, deter other males

Penis

corpora cavernosa fill w/blood

corpora cavernosa

to achieve and maintain an erection by filling with blood

Baculum

"os penis," a bone found in the penis of certain mammals, used for i.d. on species/age

Corkscrew

(hogs), compatible w/female

eutherians, penis position

anterior to scrotum

marsupials, rabbits, penis position

posterior to scrotum

Ovaries

paired, produce ova, hormones

Oviducts

uterus (embryonic development), vagina

Gonadal steroids

androgen, estrogens, and progestin

Androgens

masculinizing

Estrogens

feminizing

Progestins

assist, the hormone that plays a role in the menstrual cycle and pregnancy

Ovulation

follicle bursts with a developed egg then released into oviduct's

Capacitation

The time takes for sperm to penetrate the egg

FSH

follicle-stimulating hormone

LH

Luteinizing hormone, a hormone produced by the pituitary gland that regulates the reproductive systems in both men and women.

Corpus luteum: how is it formed

A ruptured follicle becomes the corpus luteum after it releases an egg during ovulation.

Corpus luteum: What is developed

Releases progesterone after ovulation to prepare the uterus for implantation and stimulates the mammary glands

Corpora lutea: Becomes?

Degenerate to corpora albicans (white bodies)

Corpora lutea

Temporary endocrine glands in the ovary that form after ovulation, Estradiol is produced

Estradiol

The most potent estrogen in the body, primarily used medically to treat symptoms of menopause, such as hot flashes and vaginal dryness, and to prevent osteoporosis

Estrus cycle

"heat", the female ovulates. Ready for sex and reproduction. It can be Spontaneous and induced.

Monoestrous

one heat/yr (carnivores)

Polyestrous

multiple cycles (rodents)

Implantation

The embryo attaches to the uterine wall.

Placenta: What are the functions?

1. anchors fetus

2. nutrients to the embryo

3. excretes metabolites to the mother

4. produces hormones

Placenta

A complex of embryonic/maternal tissues

Allograft

Placenta not rejected as alien due to the placenta's ability to suppress maternal immune responses

Afterbirth: Types?

expelled placenta, Placental scars, no scars

deciduous

expelled placenta

parous

Placental scars

nulliparous

no scars

Gestation: Examples of short and long?

Short in marsupials: opossum = 12.5 days, Long African elephant: 22 mos gestation

Litter reduction

Not a lot survives into weaning.

K vs r selected

Blue whale: long 10-12 mos gestation, but the same as horses. Primates: short = 60 days, long = gorillas, humans 280 d

Precocial

hatched or born in an advanced state and able to feed itself almost immediately.Newborn primates.

Delayed fertilization, for bats

copulate in Sept/Oct prior to hibernation (bats)

Spring: female ovulates, uses sperm, and birth coincides with insect emergence

blastocyst

a ball of cells that develops from a fertilized egg (zygote) about 5-6 days after fertilization

Delayed development/implantation

blastocyst stays in "neutral" for up to 7 months

Unique fertilization in Armadillos

Obligate, where a single fertilized egg splits into four genetically identical quadruplets.

Unique fertilization in Rodents

facultative, where a female can pause embryo development during lactation or stress so implantation occurs only when conditions are favorable for reproduction.

Embryonic diapause

a temporary suspension of embryonic development that occurs in certain mammals

Sliding scale of decisions for a female kangaroo

1. lose joey at foot 1st

2. lose joey in pouch 2nd

3. lose embryo in diapause

4. Stop breeding for the season

Parturition

the first stage involves dilation and effacement of the cervix, the second stage is the expulsion of the fetus through pushing and delivery, and the third stage is the delivery of the placenta then birth

Adrenal gland

secretes cortisols, which induces birth

Cortisols

a steroid hormone produced by the adrenal glands, located on top of the kidneys

Placenta: Releases?

prostaglandins

prostaglandins

causeuterine contractions

Relaxin

loosens the ligaments of the pelvis, allowing spreading for parturition

Lactation: in Bats

milk production,

-Females: functional

-Males: non-functional, except for Dayak fruit bats in Malaysia

Lysozyme

enzyme that kills bacteria/fungi

Components in Bat milk

Nutrition, passive immunity, E. coli bacteria

What type of mammals don't have teats/nipples

Monotremes

How do platypuses consume milk?

Young platypuses suck milk that drains from glands (pores in skin) to tufts of hair on the abdomen