Maternal Recognition of Pregnancy and Placentation Flashcards
What are the mechanisms of fertilization?
- Membrane receptors on an oocyte pulls in the head of the first sperm cell to make contact
- The membrane of the oocyte does not permit a second sperm head to enter
- The oocyte then undergoes its second meiotic division
- Fertilization occurs when the genetic material of a sperm combines with that of an oocyte to form a zygote
What is the zygote?
- First cell of a new individual
- The result of the fusion of DNA from sperm and egg
- The zygote begins rapid mitotic cell divisions
- The zygote stage is in the uterine tube, moving toward the uterus
What is the embryo?
- Developmental stage from the start of cleavage until the ninth week
- The embryo first undergoes division without growth
- The embryo enters the uterus at the 16-cell state
- The embryo floats free in the uterus temporarily
- Uterine secretions are used for nourishment
What is the blastocyst?
- Ball-like circle of cells
- Begins at about the 100 cell stage
- Secretes human chorionic gonadotropin (hCG) to stimulate the corpus luteum to continue producing hormones
- The blastocyst implants in the wall of the uterus (by day 14)
Describe development after implantation?
- Chorionic villi (projections of the blastocyst) develop
- Cooperate with cells of the uterus to form the placenta - The embryo is surrounded by the amnion (a fluid filled sac)
- An umbilical cord forms to attach the embryo to the placenta
What are the functions of the placenta?
- Forms a barrier between mother and embryo
- blood is not exchanged - Delivers nutrients and oxygen
- Removes waste from embryonic blood
- Becomes an endocrine organ (produces hormones) and takes over for the corpus luteum by producing:
> Estrogen
> Progesterone
> Other hormones that maintain pregnancy
Describe the fetus at the beginning of the ninth week?
- All organ systems are formed by the end of the eighth week
- Activities of the fetus are growth and organ specialization
- A stage of tremendous growth and change in appearance
What is pregnancy?
period from conception until birth
What are the anatomical changes of the mother during pregnancy?
- Enlargements of the uterus
- Accentuated lumbar curvature
- Relaxation of the pelvic ligaments and pubic symphysis due to production of relaxin
What are the physiological effects of pregnancy on the mothers GIT?
- Morning sickness is common due to elevated progesterone
- Heartburn is common because of organ crowding by the fetus
- Constipation is caused by declining motility of the digestive tract
What are the physiological effects of pregnancy on the mothers urinary system?
- Kidneys have additional burden and produce more urine
2. The uterus compresses the bladder
What are the effects of pregnancy on the mothers respiratory system?
- Nasal mucosa becomes congested and swollen
2. Vital capacity and respiratory rate increase
What are the effects of pregnancy on the mothers cardiovascular system?
- Body water rises
- Blood volume increases by 25 to 40 percent
- Blood pressure and pulse increase
- Varicose veins are common
Describe developmental aspects of the reproductive system?
- Testes form in the abdominal cavity and descend to the scrotum one month before birth
- The determining factor for gonad differentiation is testosterone - Reproductive system organs do not function until puberty
- Puberty usually begins between ages 10 and 15
- The first menses usually occurs about two years after the start of puberty - Most women reach peak reproductive ability in their late 20s
- Menopause occurs when ovulation and menses cease entirely
- Ovaries stop functioning as endocrine organs
- There is a no equivalent of menopause in males, but there is a steady decline in testosterone
