Development & Heredity Flashcards by Lilian Centeno-Perez

Prenatal Development

🔸️Pre-embryonic period
🔸️Embryonic period
🔸️Fetal period

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Prenatal Development: Pre-embryonic period

lasts for first 2 weeks after fertilization; zygote divides that implants in endometrium

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Prenatal Development: Embryonic period

extends from week 3 through 8 of gestation; embryo grows, folds, and forms rudimentary organ systems

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Prenatal Development: Fetal period

lasts from week 9 until birth; fetus grows larger and continues to develop until its organ systems can function without assistance from mother

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Fertilization

Fusion of sperm cell and secondary oocyte to form a
Zygote

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Cleavage series

of rapid mitotic divisions that produce genetically identical cells

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blastocyst outer layer of cells, called

trophoblast cells, participate in forming placenta

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blastocyst Inner cell mass called

embryoblasts, form embryo

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Implantation

Occurs approximately 4-7 days after fertilization when blastocyst begins to attach to endometrium

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Trophoblast secretes

human chorionic gonadotropin (hCG)

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human chorionic gonadotropin (hCG)

Stimulates corpus luteum in ovary to secrete estrogen and progesterone

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Progesterone maintains

endometrium

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Extraembryonic membranes
(Definition)

first appear during second week of development, continue to develop during embryonic and fetal periods

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Extraembryonic membranes what does it do?

Protecting embryo
Nutrition uptake
Gas exchange
Storage and removal of waste
Amnion

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Amnion

🔸️Encloses embryo in fluid-filled amniotic cavity; penetrated only by umbilical cord
🔸️Secretes amniotic fluid into cavity
🔸️Protects embryo from trauma and drying out

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Chorion

-outermost extraembryonic membrane

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Chorionic villi

Blood vessels

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Teratogon

Anything that causes a birth defect

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Embryonic period

starts with formation of gastrula

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organogenesis

A procces where three germ layers develop during this period (gastrula) that will become all of major organ systems

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Placenta forms during

Organogenesis this period and begins to provide nutrition and oxygen to embryo and remove wastes

Placentation

formation of placenta; attaches to uterine wall and to embryo/fetus through umbilical cord

Placenta (Definition)

organ that is shed after infant is born develops from both fetal (chorionic villi) and maternal (decidua basalis) structures

Placenta what does it do?

🔸️Site of exchange of oxygen, nutrients, and waste between mother and fetus
🔸️Produces hormones to support pregnancy
🔸️Blood Separated by placental barrier

Umbilical cord

Lconnects center of placenta to fetus umbilicus

Umbilical arteries

carry deoxygenated to placenta

Umbilical vein

Carries oxygen and nutrients toward fetal

Deoxygenated fetal blood in umbilical arteries →

placenta into chorionic villi

Oxygenated blood leaves placenta→

umbilical vein

Unique cardiovascular structures present during prenatal development:

umbilical arteries umbilical vein

Changes during Pregnancy

First trimester (1-3 months) Second trimester (4-6 months) Third trimester (7-9 months)

Changes during Pregnancy: First trimester (1-3 months)

🔸️pre-embryonic and embryonic developmentis completed and fetal development begins 🔸️By end of first trimester, basis of all of major organ systems are present making it most critical stage of development

Changes during Pregnancy: Second trimester (4-6 months)

fetus continues to grow and develop; pregnancy usually becomes obvious as uterus and abdomen expand

Changes during Pregnancy: Third trimester (7-9 months)

fetus grows rapidly and gains a significant amount of weight

Changes during Pregnancy: Second trimester (4-6 months) What happens?

🔸️Ossification begins in most bones 🔸️Genitals are distinguishable 🔸️Heartbeat can be heard with a stethoscope 🔸️Lanugo and vernix Caseosa present 🔸️Skeletal muscles begin to contract

Changes during Pregnancy: Third trimester (7-9 months) What happens?

🔸️Woman's uterus and abdomen enlarge further and many women exhibit new symptoms related to size of the fetus 🔸️Eyelids open completely 🔸️Fetus usually turns upside down 🔸️In males, testes begin to descend through inguinal canal 🔸️Fetal neurons form networks

Placenta also functions as an endocrine organ:

🔸️hCG 🔸️Human placental lactogen 🔸️Human placental prolactin 🔸️Relaxin 🔸️Leptin 🔸️Aldosterone 🔸️parathyroid hormone 🔸️Oxytocin

Placenta also functions as an endocrine organ: Human placental lactogen and placental prolactin

prepare mammary glands for milk production

Placenta also functions as an endocrine organ: Relaxin

relaxes body's muscles, joints, and ligaments

Placenta also functions as an endocrine organ: Leptin

early in preg. May have role in morning sickness, later in preg. And increases appetite

Placenta also functions as an endocrine organ: Aldosterone

Increase blood volume

Placenta also functions as an endocrine organ: Parathyroid hormone

Increases calcium absorption

Placenta also functions as an endocrine organ: Oxytocin

from fetal and maternal hypothalamus is secreted during second and third trimesters and peaks during labor to stimulate uterine contractions and allow milk release from mammary glands

Childbirth (Parturition)

Series of events collectively called labor

Childbirth (Parturition) What happens?

🔸️Both fetal and maternal hypothalamus secrete oxytocin; stimulates placenta to secrete prostaglandins 🔸️Prostaglandins dilate cervix and with oxytocin, increase strength of uterine contractions

During contractions...

🔸️As head of fetus pushes on and stretches cervix, more oxytocin is released 🔸️As more oxytocin is released, myometrium contracts more forcefully and placenta secretes more prostaglandins 🔸️Both effects cause cervix to stretch more, which stimulates release of more oxytocin (positive feedback)

Labor is a positive or negative feedback loop?

Positive feedback loop