Chapter 16 Pregnancy & Development Notice: This presentation contains actual pictures of human reproductive anatomy

Menstrual (Uterine) Cycle  Cyclic changes of endometrium  Regulated by estrogens & progesterone  Stages 1. Menses – endometrium is sloughed 2. Proliferative stage – regeneration of functional layer 3. Secretory stage –increases in size & readies for implantation  Menarche – 1 st period

Hormonal Control of Ovarian & Uterine Cycles

Hormones of Ovaries 1. Estrogens  Produced by follicle cells  Cause secondary sex characteristics 1.Development of breasts 2.Appearance of pubic hair 3.Increase in fat beneath the skin 4.Widening and lightening of the pelvis 5.Onset of menses 2. Progesterone  Produced by the corpus luteum  Production continues until LH diminishes in the blood  Helps maintain pregnancy

Mammary Glands  Present in both sexes, but only function in females - Modified sweat glands  produce milk  Stimulated by sex hormones (mostly estrogens) to increase in size

Anatomy of Mammary Glands  Areola – central pigmented area  Nipple – protruding central area of areola  Lobes – internal structures that radiate around nipple  Alveolar glands – clusters of milk producing glands within lobules  Lactiferous ducts – connect alveolar glands to nipple

Stages of Pregnancy & Development  Fertilization  Embryonic development  Fetal development  Childbirth

Fertilization  Oocyte viable hrs  Sperm viable hrs  Sperm swim to fallopian tube for fertilization  At least 20 million sperm/ml needed

Mechanisms of Fertilization  Membrane receptors of oocyte pull in head of the first sperm cell to make contact  Membrane of oocyte stops other sperm  Oocyte undergoes 2nd meiotic division  Fertilization: sperm nucleus + oocyte nucleus = zygote.

The Zygote  First cell of new individual  Zygote begins rapid mitotis  Zygote stage is in the uterine tube, moving toward the uterus

The Embryo  Developmental stage: cleavage thru 9th week  Undergoes division w/o growth at first  Embryo enters uterus at 16-cell state  Embryo floats in the uterus temporarily  Uterine secretions used for nourishment

The Blastocyst  Ball-like circle of cells  Begins at ~ 100 cells  Secretes human chorionic gonadotropin (hCG) to produce the corpus luteum to continue producing hormones (test)  Functional areas of the blastocyst -Trophoblast – large fluid-filled sphere -Inner cell mass

 The late blastocyst implants in the wall of the uterus (by day 14)  Gastrulation -Blastocyst folds in on itself -Primary germ layers formed

Derivatives of Germ Layers 1. Ectoderm  Nervous system  Epidermis 2. Endoderm  Mucosae  Glands 3. Mesoderm  Everything else

Development ( Ovulation to Implantation )

Development After Implantation  Chorionic villi (projections of the blastocyst) develop - Cooperate with cells of the uterus to form the placenta  Embryo surrounded by amnion (fluid filled sac)  Umbilical cord forms

Development After Implantation

Functions of Placenta  Barrier between mother & embryo (blood not exchanged)  Delivers nutrients & O 2  Removes waste  Becomes endocrine organ (produces hormones) and takes over for the corpus luteum  Estrogen  Progesterone  Other hormones that maintain pregnancy

The Fetus ( Beginning of the Ninth Week )  All organ systems formed by the end of the 8th week  Time for organ specialization  Stage of tremendous growth and change in appearance

Effects of Pregnancy on the Mother  Pregnancy – conception until birth  Anatomical changes - Enlargement of uterus - Accentuated lumbar curvature - Relaxation of pelvic ligaments and pubic symphysis due to production of relaxin

Effects of Pregnancy on the Mother  Physiological changes A. Gastrointestinal system  Morning sickness - elevated progesterone  Heartburn - organ crowding by the fetus  Constipation - digestive tract slows B. Urinary System  Kidneys – work more/more urine  Uterus compresses bladder

Effects of Pregnancy on the Mother C. Respiratory System  Nasal mucosa congested and swollen  Vital capacity & respiratory rate increase D. Cardiovascular system  Body water rises  Blood volume increases 25 to 40%  Blood pressure & pulse increase  Varicose veins common

Childbirth (Partition) 1. Labor – events that expel infant from uterus 2. Initiation of labor  Estrogen levels rise  Uterine contractions begin  Placenta releases prostaglandins  Oxytocin is released by the pituitary  Contractions

Labor Contractions - + Feedback

Stages of Labor

Developmental Aspects  Gender determined at fertilization - Males = XY; Females = XX - Gonads form starting week 8  Testes in abdominal cavity; descend to scrotum 1 month before birth  Testosterone determines ovaries or testes.  Reproductive organs not functional until puberty  Puberty - begins ages  1st menses occurs ~ 2 yrs after puberty starts  Peak reproductive ability - late 20s

Developmental Aspects  Menopause - ovulation & menses stop - Ovaries stop functioning as endocrine organs  No equivalent of menopause in males, but there is a steady decline in testosterone