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Human A&P BIO 304 · American River College ← Course home (Week 8)

BIO 304 . WEEK 8 . FRIDAY . LAB WORKBOOK

Pregnancy A&P (Basics)

Fertilization, implantation, the placenta, and the major changes of pregnancy.

Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.

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Part 1 of 2

Anatomy Lab

1A. What you will draw

Pregnancy is an extraordinary integration of multiple physiological systems. Today you'll draw the early events (fertilization, cleavage, implantation), then the mature placenta as the maternal-fetal interface.

Box A. Fertilization to implantation

Directions

  1. Draw a horizontal arrow with five labeled stages, left to right.
  2. Stage 1: Fertilization. A sperm meets the egg in the upper fallopian tube. Draw both with the sperm head entering the egg cytoplasm. Result: zygote (2n).
  3. Stage 2: Cleavage. Repeated cell divisions, no growth. Show a 2-cell, then 4-cell, then 8-cell embryo.
  4. Stage 3: Morula. A solid ball of about 16 cells.
  5. Stage 4: Blastocyst. A hollow ball with an inner cell mass (becomes embryo) and outer trophoblast (becomes placenta). Show a fluid-filled cavity inside.
  6. Stage 5: Implantation. The blastocyst burrows into the endometrium of the uterus around Day 6 to 7 after fertilization. The trophoblast cells invade and begin forming the placenta.
  7. Label every stage.

Box B. Mature placenta

Directions

  1. Draw a cross-section of a mature placenta and the surrounding uterine wall.
  2. Show maternal blood spaces (lacunae) in the placenta filled with maternal blood. Show the maternal arteries (spiral arteries) supplying these lacunae.
  3. Show fetal villi projecting into the maternal blood spaces. The villi contain fetal capillaries.
  4. Critical: maternal and fetal blood DO NOT MIX. They are separated by the placental barrier (trophoblast layer plus fetal capillary endothelium). Gases, nutrients, antibodies, drugs, and wastes diffuse across.
  5. Show the umbilical cord leaving the placenta, containing two umbilical arteries (carrying deoxygenated blood FROM fetus TO placenta) and one umbilical vein (carrying oxygenated blood FROM placenta TO fetus). Label.
  6. Note: this is the only place in the body where arteries carry deoxygenated blood and a vein carries oxygenated blood.

1C. Structures to label (20)

After you finish each drawing, label every structure below directly on your sketch.

  1. Zygote
  2. Cleavage
  3. Morula
  4. Blastocyst
  5. Inner cell mass
  6. Trophoblast
  7. Implantation
  8. Endometrium
  9. Placenta
  10. Maternal blood (lacuna)
  11. Spiral artery
  12. Fetal villus
  13. Fetal capillary
  14. Placental barrier
  15. Umbilical cord
  16. Umbilical artery (2)
  17. Umbilical vein (1)
  18. hCG
  19. Estrogen (placental)
  20. Progesterone (placental)

Part 2 of 2

Physiology Lab

2A. Hormonal changes through pregnancy

Sketch a graph of major pregnancy hormones over 40 weeks (gestational age) on the lines below. Then answer the interpretation questions.

1. hCG (human chorionic gonadotropin): peaks at about 8 to 10 weeks, then declines. Source? Function?
2. Progesterone: rises throughout pregnancy. Source shifts from corpus luteum to placenta around week 10. Function?
3. Estrogen: rises steadily throughout pregnancy, made by the placenta. Function in the third trimester?
4. Relaxin: produced by ovary and placenta; rises late in pregnancy. Function at parturition?
5. Oxytocin: surges at parturition. Source? Mechanism (positive feedback during labor)?
6. Prolactin: rises through pregnancy and after delivery. Function?

2B. Synthesis questions

Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.

1. Home pregnancy tests detect hCG in the urine. Explain why hCG is a reliable early marker, why it peaks at 8 to 10 weeks, and why levels in ectopic pregnancy or miscarriage are often lower than expected for gestational age.
2. Gestational diabetes develops in some women because placental hormones (especially human placental lactogen) increase insulin resistance. Predict the maternal blood glucose pattern, the consequences for the fetus (macrosomia), and why blood sugar typically normalizes after delivery.
3. Parturition (labor) involves a positive feedback loop with oxytocin. Identify the stimulus, the receptor, the response, and the amplifying step. Why is positive feedback (rather than negative feedback) the right architecture for this physiological event?

3. What to submit

Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.