A&P II Chapter 28

what is Fertilization

where sperm’s chromosomes combine with those of oocyte to form fertilized egg, called a zygote 

Where does fertilization occur?

fallopian tube, also called uterine tubes and oviduct

How do sperm get ready for fertilization 

capacitation, which enhances their motility and makes them capable of penetrating the oocyte.

Polyspermy

Multiple sperm fertilizing one egg; rare in humans but occurs in aniamls

Monospermy

Single sperm fertilizes an egg; common in humans.

Zygote

fertilized egg (diploid)

Morula

Solid ball of cells; 16 or more cells.

Blastocyst

Fluid-filled, partially hollow sphere of about 100 cells; day 4-5 later

Embryonic Development Order

Zygote, morula, blastocyst stages in sequence.

Endoderm specialization major event

The primitive gut is formed from the endodermal folding. The organs of the GI tract are apparent, and glands arise. The mucous lining of the respiratory tract forms in the pharyngeal endoderm(forgut)

Ectoderm specialization major event

Neurulation: first major event of organogenesis where the formation gives rise to the brain and spinal cord

Mesoderm specialization major event

Somites (where vertebrae and ribs are formed), Intermediate mesoderm (where gonads and kidneys are formed)and Lateral plate mesoderm (which forms the heart, blood vessels, and most of the connective tissues of the body and entire wall of the digestive and respiratory organs)

What occurs in somites at the mesoderm?

vertebrae and ribs are formed at the sclerotomes, the dermis of the dorsal body region is formed at the dermomyotomes, and trunk and limb musculature are formed at the myotomes.

What occurs in Intermediate mesoderm at the mesoderm?

gonads and kidneys are formed

What occurs in lateral plate at the mesoderm?

heart, blood vessels, and most of the connective tissues of the body and entire wall of the digestive and respiratory organs are formed

What is ectoderm's major derivatives

epidermis, hair, nails, glands of skin, brain, and spinal cord. Finally neural crest and derivatives (e.g., cranial, spinal, and sympathetic ganglia and associated nerves; chromaffin cells of the adrenal medulla; pigment cells of the skin) 

What is endoderm's major derivatives

Epithelial lining and glands of digestive and respiratory tract

What is endoderm's major derivatives

• Notochord: nucleus pulposus of intervertebral disc 

• Somite 

• Sclerotome vertebrae and ribs 

• Dermatome: dermis of dorsal body region 

• Myotome trunk and limb musculature 

• Intermediate mesoderm 

• Kidneys 

• Gonads 

• Lateral Plate mesoderm 

• Somatic mesoderm 

• Parietal serosa 

• Dermis of ventral body region 

• Connective tissue of limb (bones, joints, ligaments) 

• Splanchnic mesoderm 

• Wall of digestive and respiratory tract (except epithelial lining) 

• Visceral serosa  

• Heart 

• Blood vessels 

Notochord purpose

Serves as the first axial support of the embryo.  

What does the Notochord transform into

The vertebral column in vertebrates. ( the spine)

Embryonic disc purpose

Forms the embryo and extraembryonic membranes

What does the embryonic disc transform into

two to three of the germ layers

Primitive Streak purpose

Establishes embryo's longitudinal axis

What does the primitive streak transform into

the epithelial line of the digestive system, respiratory system, urogenital system and their associated glands

primitive gut purpose

forms the epithelial lining of the GI tract 

What does the primitive gut transform into

The digestive system (tract) organs (esophagus, stomach, intestines, and associated organs like the liver and pancreas)

Neural Tube purpose

gives rise (foundation ) to the brain, rest of natural tube (spine) 

What does the neural tube transform into

the brain and spinal cord

What is the placenta?

Temporary organs that is formed from embryonic and maternal tissues. 

Placenta purpose

Provides nutrients and oxygen to the developing fetus, removes waste products 

Placenta function during pregnancy

Nutritive, respiratory, excretory, endocrine functions 

How long does it take for the placenta to be fully formed

3 months

Hormone secretions that occur in the placenta during pregnancy

• HCG from the beginning of pregnancy until the production of estrogen and progesterone increases. This promotes placental development 

• It also secretes Human placental lactogen, human chorionic thyrotropin and relaxin These hormones regulate metabolism, support fetal growth, and help maintain pregnancy.

Human Chorionic Gonadotropin (hCG)

Hormone maintaining corpus luteum during early pregnancy and continue the secretion of progesterone and estrogen.

What structure does hCG impact

Corpus luteum

Progesterone

Hormone maintaining pregnancy; prepares mammary glands.

What structure does progesterone impact

uterus and mammary gland

Estrogen

Hormone promoting fetal organ growth and maternal tissue. It also prepares the uterus for childbirth with dilation and contractions in the uterus

What structure does estrogen impact

Breasts, uterus, the pelvis and joints 

Human Placental Lactogen (hPL)

Stimulates the maturation of breasts, promotes fetal growth, decrease gestational diabetes mellitus, and reserves glucose for fetus

What structure does hPL impact

breasts and uterus

Stages of Labor

Dilation, expulsion, and placental

Dilation Stage

First labor stage: cervix fully dilates to 10cm. This is where engagement occurs (basically the head about to leave the coochie )  

Expulsion Stage

Second labor stage: baby is delivered either in vertex position (headfirst) or breech position (butt first). Where crowning and expulsion happen

Placental Stage

Final stage; placenta delivered within 30 minutes.

Umbilical Arteries

Carry oxygen-poor blood from fetus to placenta.

what does Umbilical Arteries transform into after birth

median umbilical ligaments

Umbilical Vein

Carries oxygen-rich blood from placenta to fetus.

what does Umbilical Vein transform into after birth

ligamentum

what does Ductus Venosus transform into after birth

ligamentum venosum

what does Ductus Arteriosus transform into after birth

ligamentum arteriosum.

Which vascular modification in the fetus rapidly becomes non-functional

Umbilical arteries,  Umbilical vein, Ductus venosus, and Ductus Arteriosus 

What does the Forman Ovule changes/tranforms into?

fossa ovalis after birth.

Which vascular modification in the fetus take 6 months to a year to become non-functional

Forman ovule

Forman ovule

opening in interatrial septum of heart that allows blood to bypass pulmonary circulation 

Ductus venosus 

bypasses liver; umbilical vein drains into ductus venosus which empties into inferior vena cava 

Ductus Arteriosus 

bypasses pulmonary circulation; pulmonary trunk drains into ductus arteriosus, which drains into aorta 

What is going on in lactation

It is the production of milk by the mammary glands

What is made in the first few days after the birth of an infant in the mammary gland?

Colostrum

What are the respiratory system physiologic changes that occurs in females during pregnancy

• Estrogens may cause nasal edema and congestion 

• Tidal volume increases, and dyspnea (difficult breathing) may occur later in pregnancy 

What are the gastrointestinal system physiologic changes that occurs in females during pregnancy

• Morning sickness is believed to be due to elevated hCG, estrogen and progesterone levels 

• Heartburn and constipation more common 

What are the urinary system physiologic changes that occurs in females during pregnancy

• Increased urine production due to increased maternal metabolism and fetal wastes 

• Frequent, urgent urination and stress incontinence may occur as bladder is compressed as fetus grows 

What are the cardiovascular system physiologic changes that occurs in females during pregnancy

• Blood volume increases 25–40% to safeguard against blood loss during childbirth 

• Cardiac output rises up to 35-40% to propel greater volume around body  

• Venous return from lower limbs may be impaired, resulting in varicose veins 

• Some undifferentiated fetal stem cells can enter maternal circulation 

•  Can integrate into maternal tissue 

•  Consequences to mother unknown 

• May play a role in autoimmune diseases or be beneficial