Anatomy and Physiology: Conception & Pregnancy Flashcards
Pelvis
- Protection of the pelvic structures
- Accommodation of the growing fetus
- Anchorage of pelvic support structures
- Divided into false & true pelvis
- false pelvis is above the linea terminalis (inlet)
- true pelvis is below
Spermatogenesis
- Complete spermatogenesis takes 74 days, producing 300-400 million/day
- upon ejaculation (3-5 ml), most sperm do not survive more than 48 hours within the female reproductive tract - only 50,000 - 100,000 reach the ovum
- the alkaline nature of sperm protects them from vaginal acidity
- Composition of Semen: 60% seminal vesicular fluid, 30% prostatic fluid, 10% sperm and spermatic duct secretions
How does the scrotum maintain temp?
- The scrotum maintains a temperature 2-3 degrees lower than the body, which is critical for spermatogenesis
- Cremaster muscle contracts and relaxes testes closer and further from the body
- Dartos muscle contracts scrotum to be wrinkled, which decreases its surface area
- Pampiniform plexus: vein network cools arterial blood
Oogenesis
Primary oocyte: 2 million are formed during fetal development
Secondary oocyte: develops and starts meiosis monthly
- Second meiosis is only completed when fertilized = zygote
- optiman fertility is 17-28 years old and starts to decrease at 35
Menstrual Cycle
- purpose is to prepare the uterus for pregnancy
- Starts 14 days after ovulation (usually every 28 days)
- Hypothalamic-pituitary cycle
- Ovarian cycle
- Endometrial cycle
Hypothalamic-Pituitary Cycles
- End of cycle = decrease in Progesterone & Estrogen from hypothalamus
- The release of Gonadotropin-releasing hormone (GnRH) stimulates LH & FSH
- Luteinizing Hormone: rupture of follicle and conversion of ovum to the corpus luteum
- Follicle Stimulating Hormone: starts at menstruation causing ovum to mature
Unterine/Endometrial Cycle
- Proliferative Phase: estrogen causes proliferation of ovarian mucosa until ovulation
- Secretory Phase: progesterone causes maturation and secretion by uterine glands - until about 3 days prior to onset of menses
- ischemic phase: blood supply to lining stops and lining prepares to slough
Ovarian Cycle
- Follicular phase: 1-30 ova develop, estrogen increases = one ovum released
- Ovulation - day 14 mature ovum
- Luteal phase: the follicle develops into the corpus luteum, increased progesterone maintains the uterine lining
- Ischemic Phase: progesterone falls
Fertilization and Implantation
- fertilization can happen anywhere in the fallopian tube
- Not every fertilized ovum = a pregnancy
- implantation happens between 6 and 10 days after conception
Implantation
- implantation occurs 6-10 days post-fertilization
- trophoblast: secretes enzymes to burrow into endometrium
- trophoblast develops chorionic villi to act as vascular processes for O2/nutrients and CO2/waste disposal
- Endometrium terminal decidua - under chorionic villi is the decidua basalis
- Prefers anterior or posterior fundal height
- chorionice villi are tiny projections of placenta tissue that look like fingers and contain the same genetic material as the fetus
Trophoblast
a thin layer of cells that helps a developing embryo attach to the wall of the uterus, protects the embryo, and forms a part of the placenta
Decidua basalis
the portion of the decida that is related to the chorion and participates with it in the formation of the placenta, becoming the maternal component of the fully formed placenta
- endometrium decidua: connecting to growing lump of cells. wants to implant on the front or back of uterus
Gestational Age
- Weeks of pregnancy is always counted from the women’s last menstrual period (LMP)
- Since ovulation doesn’t occur until Day 14, the moment fertilization occurs, the zygote is already considered to be at 2 week gestational
- When the women misses her fist period (approx day 28), the embryo has been developing for 2 weeks but is considered 4 weeks gestational age
Naegle’s Rule
first day of LMP, add one year, subtract three months, add seven days
3 phases of Fetal Development
Pre-embryonic
Embryonic
Fetal
Pre-embryonic
- Conception to Day 14
- Prior to placental function, it is a cavity that forms, helps transport maternal nutrients and oxygen to the embryo via diffusion
- Creates blood cells and plasma
- Cellular replication, blastocyst formation, initial development of embryonic membranes, primary germ layers
- During embryongenesis, three germ layers form as the source of all embryo tissues and organs: ectoderm, mesoderm, endoderm