Maternal and Child Nursing (Midterm)

Study Notes

During the first four days of life, cells in a zygote are termed totipotent stem cells.
Within the next four days, the zygote becomes an embryo.
Cells undergo differentiation and lose their ability to become any body cell.
Pluripotent stem cells are capable of becoming specific body cells, such as nerve, brain, or skin cells.
As development progresses, cells become increasingly specific, eventually becoming multipotent or committed to a specific body organ.

Fetal development proceeds in a cephalocaudal direction, with the head developing before the lower extremities.
This pattern continues after birth, as infants can lift their heads before they can walk.
As a fetus grows, body organ systems develop from specific tissue layers called germ layers.

The blastocyst contains three primary germ layers:
- Ectoderm: Forms the outer layer of the blastocyst and develops into the central nervous system, peripheral nervous system, skin, hair, nails, and other structures.
- Mesoderm: Forms the middle layer of the blastocyst and develops into supporting structures of the body, such as connective tissue, bones, cartilage, tendons, muscles, and the circulatory system.
- Endoderm: Forms the inner layer of the blastocyst and develops into the linings of the gastrointestinal, respiratory, and urinary tracts.

Organogenesis refers to the formation of organs.
All organ systems are complete, at least in a rudimentary form, by the end of the embryonic period (8 weeks' gestation).
During this time, the developing fetus is highly vulnerable to teratogens, which can adversely affect development.
Teratogens include factors like cigarette smoking.

The cardiovascular system is one of the first to become functional during intrauterine life.
A single heart tube forms by the 16th day of life.
The first heartbeat occurs around the 24th day.
The septum dividing the heart develops between the 6th and 7th week.
Heart valves begin to develop in the 7th week.
A heartbeat can be heard by a Doppler instrument between the 10th and 12th week.
The sympathetic nervous system matures around the 28th week, stabilizing heart rate to 110-160 beats per minute.

The blood oxygen saturation level of the fetus is about 80% of a newborn's saturation level.
The rapid fetal heart rate (120-160 beats per minute) is necessary to supply oxygen to cells due to the lower oxygen saturation of fetal red blood cells.

Fetal hemoglobin (HbF) has two alpha and two gamma chains, making it more concentrated and having a greater affinity for oxygen than adult hemoglobin.
Adult hemoglobin (HbA) has two alpha and two beta chains.

The respiratory and digestive tracts exist as a single tube during the 3rd week of intrauterine life.
A septum begins to divide the esophagus from the trachea during the 4th week, and lung buds appear on the trachea.
The diaphragm does not completely divide the thoracic cavity from the abdomen until the 7th week.
Failure of the diaphragm to close completely can lead to a diaphragmatic hernia, where organs like the stomach, spleen, liver, or intestines may be pulled up into the thoracic cavity.
Alveoli and capillaries begin to form between the 24th and 28th week.
Spontaneous respiratory practice movements begin around 3 months of gestation.
Surfactant is a phospholipid substance that reduces alveolar surface tension on expiration, preventing alveolar collapse and improving an infant's ability to maintain respirations in the outside environment.
Surfactant consists of lecithin and sphingomyelin.
In early surfactant formation, sphingomyelin is the primary component.
Around 35 weeks of gestation, there is a surge in lecithin production, leading to an L/S ratio of 2:1.

During the 3rd week of gestation, the neural plate, a thickened portion of ectoderm, forms.
The top portion of the neural plate develops into the neural tube, which forms the CNS.
The neural crest forms the PNS.
All parts of the brain (cerebrum, cerebellum, pons, and medulla oblongata) develop in utero but are not fully mature at birth.
Brain growth continues at high levels until 5-6 years old.
By 24 weeks of gestation, the brain has developed enough that the fetus can experience pain.