Human Physiology

Question 1

What are the three phases of sex determination and differentiation?

Answer 1

1. Fertilization of ovum by sperm
2. Two phases during embryonic life

These phases involve genetic, gonadal, and phenotypic development.

Question 2

What are the sex chromosomes labeled as?

Answer 2

X and Y chromosomes

These chromosomes play a major role in sex determination.

Question 3

What is the chromosomal configuration for females and males?

Answer 3

Females: XX, Males: XY

This configuration determines the genetic sex of an individual.

Question 4

During meiosis, how many chromosomes do daughter cells contain?

Answer 4

22 autosomes and 1 sex chromosome

This applies to both sperm and ovum.

Question 5

What does the Y chromosome contribute to in terms of sex determination?

Answer 5

Production of testes and masculine nature

The presence of Y chromosome is necessary and sufficient for maleness.

Question 6

What is the function of the SRY gene on the Y chromosome?

Answer 6

Causes differentiation of indifferent gonad to embryonic testis

This gene is crucial for the development of male characteristics.

Question 7

What is the primitive gonad referred to before the 6th week of gestation?

Answer 7

Bipotential gonad

It is identical in both sexes and consists of germ cells, coelomic epithelium, and mesenchymal cells.

Question 8

Fill in the blank: The last pair of chromosomes in humans, which play a major role in sex determination, are called _______.

Answer 8

sex chromosomes

Question 9

True or False: The autosomes play a role in sex determination.

Answer 9

False

Only the sex chromosomes (X and Y) are involved in sex determination.

Question 10

What is the role of the H-Y Antigen in sex differentiation?

Answer 10

Initiates differentiation of bipotential gonad to male gonad

This process occurs through the action of the SRY gene.

Question 11

What happens during fertilization in terms of chromosome composition?

Answer 11

Resulting zygote contains 22 autosomes and one pair of sex chromosomes (XX or XY)

This composition determines the genetic sex of the zygote.

Question 12

What develops in genetic males during the 7th to 8th week after gestation?

Answer 12

Fetal testis

This development is influenced by testis determining genes from the SRY chromosome.

Question 13

What are the main cell types present in the fetal testis?

Answer 13

• Spermatogonic cells
• Sertoli cells
• Leydig cells

These cells are essential for the development of male reproductive structures.

Question 14

What is the role of SRY in gonadal development?

Answer 14

Determines the development of fetal testis

The SRY gene is crucial for male sex determination.

Question 15

What happens in the absence of the SRY chromosome?

Answer 15

Differentiation into fetal ovary

This occurs in genetic females, leading to female reproductive structures.

Question 16

What are the two genital ducts that develop during the sexually indifferent stage?

Answer 16

• Wolffian duct
• Mullerian duct

These ducts are crucial for the development of male and female reproductive systems.

Question 17

What do Sertoli cells secrete when fetal testis development is complete?

Answer 17

Mullerian Inhibitory Peptide (MIS)

MIS causes the regression of the Mullerian duct.

Question 18

What hormone do Leydig cells secrete, and what is its role?

Answer 18

Testosterone

Testosterone causes differentiation of male genital tract and male external genitalia from the Wolffian duct.

Question 19

What does the Wolffian duct develop into in the presence of testosterone?

Answer 19

• Seminal vesicle
• Vas deferens
• Epididymis

These structures are integral to the male reproductive system.

Question 20

Fill in the blank: The regression of female secondary sex organs is caused by _______.

Answer 20

MIS

MIS is critical in preventing the development of female reproductive structures in genetic males.

Question 21

What are the consequences of the secretion of MIS and testosterone in genetic males?

Answer 21

• Regression of Mullerian duct
• Development of male genital tract
• Development of male external genitalia

These processes are essential for male sexual differentiation.

Question 22

What is the function of the genital tubercle in male development?

Answer 22

Forms parts of the external genitalia

The genital tubercle contributes to the formation of the penis.

Question 23

True or False: The presence of the Mullerian duct is necessary for the development of male reproductive organs.

Answer 23

False

The Mullerian duct regresses in males due to the action of MIS.

Question 24

What happens if there is determination of genetic female?

Answer 24

There is no development of male gonad from bipotential gonad, leading to differentiation of female gonad (ovary), degeneration of Wolffian duct, and development of Mullerian ducts to female external genitalia.

Question 25

What is spermatogenesis?

Answer 25

Spermatogenesis is the process by which spermatogonia are differentiated into spermatozoa or viable sperms.

Question 26

Where are spermatogonia located?

Answer 26

Spermatogonia are located in 2-3 layers on the basement membrane of the germinal epithelium of the seminiferous tubules of the testis.

Question 27

What are Type A spermatogonia?

Answer 27

Type A spermatogonia are diploid (44 + XY) cells that proliferate by mitotic divisions to form Type B spermatogonia.

Question 28

What is the duration of spermatogenesis?

Answer 28

Spermatogenesis requires about 74 days.

Question 29

What occurs during spermatocytogenesis?

Answer 29

Type B spermatogonia divide mitotically to form a large number of primary spermatocytes, which then undergo meiotic division.

Question 30

What happens during the meiotic phase of spermatogenesis?

Answer 30

Primary spermatocytes undergo meiotic division, reducing the chromosome number to haploid and forming secondary spermatocytes.

Question 31

What is spermiogenesis?

Answer 31

Spermiogenesis is the sequence of developmental events by which spermatids are transformed into mature sperm without further cell division.

Question 32

What are the major features of spermiogenesis?

Answer 32

Major features include condensation of chromatin, changes in the shape and size of the nucleus, and loss of excess cytoplasm.

Question 33

What is the effect of testosterone on muscle?

Answer 33

Increases muscle mass due to increase in protein synthesis.

Question 34

What are the effects of testosterone on bone?

Answer 34

Increases thickness of bone, deposition of Ca salts, quantity of bone matrix, and makes the pelvis funnel shaped. Increases strength of entire pelvis and causes the epiphyses to fuse to the long bone, thus stopping linear growth.

Question 35

How does testosterone affect BMR?

Answer 35

Increases BMR indirectly by increasing anabolic activity of protein.

Question 36

What is the effect of testosterone on RBCs?

Answer 36

Increases RBC count by increasing the size of the kidney, metabolic rate, and erythropoiesis.

Question 37

What is the effect of testosterone on water and electrolyte balance?

Answer 37

Increases retention of salt and water by the kidneys.

Question 38

How is testosterone secretion regulated?

Answer 38

Regulated mainly by the hypothalamo-hypophyseal testicular axis and negative feedback by testicular hormones.

Question 39

What is the role of GnRH in testosterone secretion?

Answer 39

Cells of arcuate nuclei of hypothalamus secrete GnRH, stimulating the release of FSH and LH from anterior pituitary gonadotrophic cells, which in turn stimulates Leydig cells to secrete testosterone.

Question 40

How does testosterone exert negative feedback?

Answer 40

When testosterone levels in blood increase, it inhibits both anterior pituitary and hypothalamus to release LH, FSH, and GnRH.

Question 41

What is the role of inhibin in testosterone regulation?

Answer 41

Inhibin, secreted by Sertoli cells under the influence of FSH, inhibits the release of FSH and LH from anterior pituitary, thus inhibiting testosterone secretion.

Question 42

What are the female sex hormones?

Answer 42

Estrogen, progesterone, and relaxin.

Question 43

What is the source of estrogen?

Answer 43

Theca interna of graafian follicle (major), granulosa cell of graafian follicle, placenta, and adrenal cortex.

Question 44

What are the effects of estrogen on the genital system?

Answer 44

Increases size and functional capabilities of uterus, ovary, fallopian tube, vagina, and external genitalia. Changes cuboidal epithelial cells of vagina to stratified for increased resistance to trauma and infection.

Question 45

What is the effect of estrogen on the breast?

Answer 45

Causes development of stromal tissues of breast and growth of ductile system.