Chapter 16Pregnancy & Development

Notice: This presentation contains actual pictures of human reproductive anatomy

Menstrual (Uterine) CycleMenstrual (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 – 1st period

Hormonal Control of Ovarian & Uterine CyclesHormonal Control of Ovarian & Uterine Cycles

Hormonal Control of Ovarian & Uterine CyclesHormonal Control of Ovarian & Uterine Cycles

Hormones of OvariesHormones of Ovaries1. 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 GlandsMammary 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 GlandsAnatomy 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 & DevelopmentStages of Pregnancy & Development

Fertilization

Embryonic development

Fetal development

Childbirth

FertilizationFertilization Oocyte viable 12 - 24 hrs

Sperm viable 12 - 48 hrs

Sperm swim to fallopian tube for fertilization

At least 20 million sperm/ml needed

Mechanisms of FertilizationMechanisms 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 ZygoteThe Zygote First cell of new individual

Zygote begins rapid mitotis

Zygote stage is in the uterine tube, moving toward the uterus

The EmbryoThe 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 BlastocystThe 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 LayersDerivatives of Germ Layers

1. Ectoderm

Nervous system

Epidermis

2. Endoderm

Mucosae

Glands

3. Mesoderm

Everything else

Development (Development (Ovulation to ImplantationOvulation to Implantation))

Development After ImplantationDevelopment 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 ImplantationDevelopment After Implantation

Functions of PlacentaFunctions of Placenta Barrier between

mother & embryo (blood not exchanged)

Delivers nutrients & O2

Removes waste

Becomes endocrine organ (produces hormones) and takes over for the corpus luteum

Estrogen

Progesterone

Other hormones that maintain pregnancy

The Fetus (The Fetus (Beginning of the Ninth WeekBeginning 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 MotherEffects 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 MotherEffects 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 MotherEffects of Pregnancy on the MotherC. 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)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 LaborStages of Labor

Developmental AspectsDevelopmental 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 10 - 15

1st menses occurs ~ 2 yrs after puberty starts

Peak reproductive ability - late 20s

Developmental AspectsDevelopmental 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