IGCSE Biology Paper-3: Specimen Questions with Answers 281 - 282 of 358

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Fig. is a diagram of a fetus in the uterus.

Question 281 (1 of 3 Based on Passage)

Short Answer▾

Describe the process of Let Down reflex in human female.

The mammary glands of the female undergo differentiation during pregnancy and starts producing milk towards the end of pregnancy by the process called lactation.
This helps the mother in feeding the new- born.
The milk produced during the initial few days of lactation is called colostrum which contains several antibodies essential to develop resistance for the new-born babies.
Breast-feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.

Short Answer▾

Table shows one of the names and the functions of some of the labelled parts shown in Fig.

Complete Table using the information in Fig.

One of the Names and the Functions of Some of the Labelled Parts
name of part	letter in Fig.	function
amniotic sac		contains amniotic fluid
		carries materials betweenmother and fetus
		dilates during birth

One of the Names and the Functions of Some of the Labelled Parts
name of part	letter in Fig.	function
amniotic sac	B	contains amniotic fluid
placenta	D	carries materials between mother and fetus
cervix	C	dilates during birth

After implantation, finger-like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood.
The chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between developing embryo (fetus) and maternal body called placenta.
The placenta facilitates the supply of oxygen and nutrients to the embryo and removal of carbon dioxide and excretory/waste materials produced by the embryo.
The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.
Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG) , human placental lactogen (hPL) , estrogens, progestogens, etc.
In the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary.
Let us remember that hCG, hPL and relaxin are produced in women only during pregnancy.
In addition, during pregnancy the levels of other hormones like estrogens, progestogens, cortisol, prolactin, thyroxine, etc. , are increased. (essential for supporting the fetal growth, metabolic changes in the mother and maintenance of pregnancy) .