ORIGIN AND DEVELOPMENT OF ORGAN SYSTEM

Question 1

4 days of life zygote cells are termed TOTIPOTENS STEM CELLS (undifferentiated cells) and has potential to grow into any cell in the human body
next 4 days embryo cells begin to show differentiation
few more days and they specifically grow into a particular body organ

Answer 1

i. stem cells

Question 2

as soon as conception takes place, development proceeds in a cephalocaudal direction

Answer 2

ii. zygote growth

Question 3

(outermost layer): develops into the nervous system, the integumentary system, the sense organs, and mammary glands

Answer 3

ectoderm

Question 4

(middle layer): develops into supportive structures of the body: connective tissue, bone cartilage; kidney and urethra; reproductive system; heart, lymph, circulatory systems, and blood cells)

Answer 4

mesoderm

Question 5

(innermost layer): develops into the lining of the gastrointestinal and respiratory tracts as well as the tonsils, thyroid, parathyroid, and thymus glands. Also develops the lower urinary system (bladder and urethra)

Answer 5

endoderm

Question 6

by the end of 8th week gestation all organ systems are complete; vulnerable to invasion of teratogens (cigarette smoking and alcohol ingestion)

Answer 6

organogenesis (organ formation)

Question 7

one of the first systems to become functional in intrauterine life

Answer 7

iv. circulatory system

Question 8

network of blood vessels and single heart tube is formed

Answer 8

16th day of life:

Question 9

positive heartbeat;

Answer 9

24th day:

Question 10

septum that divides hearts into chambers develops

Answer 10

6th-7th week:

Question 11

heartbeat may be heard by using a doppler instrument
heart rate of the fetus is affected by: oxygen level activity and circulating blood volume

Answer 11

10th-12th week

Question 12

sympathetic nervous system matures and the heart rate stabilizes (normal HR: 110-160 bpm)

Answer 12

28th week:

Question 13

fetus is connected by umbilical cord to the placenta
through the blood vessels in the umbilical cord, the fetus receives all the necessary nutrition, oxygen, and life support from the mother through the placenta
waste products and carbon dioxide from the fetus are sent back through the umbilical cord and placenta to the mother’s circulation to be eliminated
fetal circulatory system uses two right to left shunts (2 shunts in the heart and 1 shunt in the lungs) (small passages that direct blood that needs to be oxygenated.) purpose of these shunts is to bypass certain body parts in particular, the lungs and the liver that are not fully developed while the fetus is still in the womb
the shunts that bypass the lungs are called the foramen ovale, which moves blood from the right atrium of
the heart to the left atrium while the ductus arteriosus moves blood from the pulmonary artery to the aorta;

Answer 13

v. fetal circulation

Question 14

respiratory and digestive tract exists as a single tube

Answer 14

3rd week of intrauterine life:

Question 15

septum begins to divide the esophagus from the trachea and lung buds appear on the trachea

Answer 15

end of 4th week:

Question 16

spontaneous respiratory practice movements begin and continue throughout pregnancy; specific lung fluids with a low surface tension and low viscosity forms in alveoli to aid in expansion of alveoli at birth (rapidly absorbed at birth)

Answer 16

early 3 months gestation

Question 17

SURFACTANT, a phospholipid substance, formed and secreted by the alveolar cells of the lungs + it decreases alveolar surface tension on expiration, preventing alveolar collapse and improving the infant’s ability to maintain respirations in the outside environment

Answer 17

24th wee