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MCAT Biology and Biochemistry > Reproduction > Flashcards

Reproduction Flashcards

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1
Q

What is Meiosis? The phases of meiosis?

A

Meiosis is the process of making haploid germ cells from diploid cells.
- Meiosis 1 - The reduction from diploid to haploid.
- Meiosis 2 - creation of 4 haploid cells

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2
Q

What special event happens during prophase 1 of meiosis 1?

A

Recombination. Homologous chromosomes come together to form the synaptonemal complex ( tetrad) and genes cross over at the chisma.

genes further apart are less linked and cross over at a higher probability.

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3
Q

Describe the stages of meiosis 1

A

Prophase 1- nuclear envelope breaks down, chromosomes condense, process of recombination.

Metaphase 1- homologous chromosomes line up alongside the metaphase plate

Anaphase 1 - the homologous chromosomes are pulled apart to opposite sides of the cell.

Telophase & Cytokenesis - nuclear envelope redevelops, chromosomes decondense, and diploid cell splits into 2 haploid cells.

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4
Q

Hemizygous

A

When you have one allele for a gene.

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5
Q

Are biological sex is determined by what pair of chromosomes?

A

23rd pair when shown of karyotype.

XY- males
XX- Females

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6
Q

What gene determines male development?

A

SRY gene which is located on the Y chromosome

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7
Q

What are the 2 functional groups of the male gonads?

A

Seminiferous tubules which produce sperm, they’re nourished by sertoli cells.

leydig interstital cells which secrete testosterone and other male androgens.

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8
Q

Role of Seminal vesicles, prostate glands, and bulbrothral glands of the male gonads.

A
  • Seminal vesicles - create fructose to power sperm’s flagellum.
  • Prostate gland- provides sperm a slight alkalinity so it can survive in acidic environment of the vagina.
  • bulbrotheral gland - produce liquid lubricates and cleans out urethra.
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9
Q

What is the path sperm takes to exit the penis?

A

SEVE(N) UP
- Seminiferous tubules
- Epididymus
- vas deferens
- Ejaculatory ducts
- urethra
- penis

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10
Q

Describe the process of spermatogenesis

A

Diploid cells are spermatogonia –) undergo mitosis to become primary spermatocytes—) first meiotic division is to secondary spermatocytes—) second meiotic division is to spermatids which undergoes maturation to become spermatozoa.

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11
Q

What are the 4 parts of sperm?

A
  • Head ( contains the acrosome) which serves to break through the female ovum.
  • Midpiece - contains mitochondria which contains fructose to power the flagella via ATP.
  • tail- used for movement
  • endpiece- end part of the tail
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12
Q

What is the female reproductive system called?

A

There gonads are called the ovaries.

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13
Q

Once a month an egg is released from the ovaries how is this achieved?

A

cilia hairs brushes the egg form the peritoneal cavity into the fallopian tubes where it waits to get fertilized.

The cervix is below the uterus and is semen is deposited.

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14
Q

Describe the process of oogenesis

A

Produces female ovum.

  1. oogonium undergoes mitosis to become a primary ooctye ( arrested in prophase 1 until menstrual cycle)
  2. primary ooctye undergoes meiosis I to become secondary ooctye and the 1st polar body ( which is arrested in metaphase II until fertilization).
  3. secondary oocyte finishes. meiosis 2 to become ovum ( ovum = fertilized ooctye)
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15
Q

What protects the ooctye?

A

2 layers. 1st layer is the corona radiata and the second layer is the zona pellucida. This two layers are made of glycoproteins.

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16
Q

When we hit puberty which hormones are released to develop and maintain the reproductive system?

A

Gonadotropin- releasing hormone ( GnRH) is released from the hypothalamus and travels to the anterior pituitary where LH and FSH are released.
- In males LH acts on interstitial leydig cells which secretes testosterone and FSH which activates sertoli cells which aids in sperm maturation.
- testosterone is responsible for male characteristics like a deep voice ( has a negative feedback on hypothalamus and anterior pituitary)

  • female ovaries released estrogen which is responsible for female characteristics like widening of the hips, development of breasts, etc.
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17
Q

Describe the menstrual cycle in females.

A
  1. Follicular phase- the endometrial lining is shed from the previous cycle). Estrogen and Progesterone levels fall has GnRH, FSH, LH levels increase causing the formation of ovarian follicles. They secrete estrogen which exerts a negative feedback on the hypothalamus and A. pituitary.
  2. Ovulation- Once estrogen reach certain levels it switches to positive feedback and increases release of hormones from hypothalamus and A. pituitary. The increase in LH in particular causes the release of the ooctye into peritoneal cavity.
  3. Luteal phase- the ruptured follicular cells come together to form corpus leuteum which secretes progesterone. This exerts a negative feedback on hypothalamus and A. pituitary so that another ooctye is not released.
  4. If pregnancy occurs the zygote divides into a blastocyst and implant into the uterine wall and secretes HCG which maintains the corpus leuteum ability to secrete progesterone until the third trimester in which the placenta can make progesterone on its on. If it doesn’t occur than corpus leuteum loses it’s ability to secrete progesterone and the lining decreases. The negative feedback is also disresupted and so high levels of hormoes results and the cycle starts over.
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18
Q

Menopause

A

When a women ages her ovaries become less sensitive to FSH and LH.

Estrogen and progesterone levels drop and FSH and LH levels rise due to the inability to exert negative feedback this causes high levels of both hormones in the blood.

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19
Q

Fertilization of the ovum by sperm

A

Sperm combines with ovum in the ampulla of the fallopian tube.

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20
Q

Acrosomal Apparatus

A

When sperm penetrates the corona radiata and the zona pellucida and forms the acrosomal apparatus and injects it’s pronucleus.

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21
Q

Cortical reaction

A

When the acrosomal apparatus forms it releases calcium ions which increase the metabolism of the zygote and to prevent sperm from further penetrating it.

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22
Q

Fraternal ( dizygotic ) twins v. Identical ( monozygotic) twins

A

Fraternal twins results from 2 different sperm penetrating two different ovum.

Identical twins results from splitting of the zygote. ** Identical twins can be identified by having identical placental structures**

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23
Q

Cleavage ( intermediate v. Determinate)

A

The division of embryonic stem cells of the zygote ( from there it’s morula and then blastula).
- Intermediate - cells can become any cell in the body.
- Determinate- cells become a specific type of cell.

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24
Q

Blastocyst

A

Results from division of zygote to morula and morula to blastocyst.

The blastocyst contains the blastocoel which is the fluid filled center and 2 different cell types.

Blastula implants into uterine wall to form the placenta.

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25
Q

Chorion

A

Contains the chorionic villi which penetrates the endometrial layer and creates interface between maternal and fetal blood.

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26
Q

Yolk sac

A

Sac that holds the fetus

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27
Q

Allantois

A

Allows fluid exchange between the yolk sac and embryo.

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28
Q

Amnion

A

Located outside of chorion creates amniotic fluid.

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29
Q

What connects the embryo to the placenta?

A

Umbilical cord

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30
Q

What is gastrulation?

A

The formation of the 3 germ layers from the blastocyst.

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31
Q

Describe the structures of the blastula ( blastocyst)

A

The archenteron is the center of the blastula and the opening is the blastopore. Ectoderm on the outside of blastula, endoderm is on the inside, and mesoderm in the middle.

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32
Q

What structures form from the following germ layers?
- Ectoderm
- Mesoderm
- Endoderm

A
  • Ectoderm - forms more “ outside” structures like th epidermis, hair/skin/ nails. epithelia, and the nervous system.
  • Mesoderm- more “ middle structures” like musculoskeletal system, circulatory system, excretory system, connective tissue, gonads.
  • Endoderm - epithelial lining of respitory system, digestive system, and other organs.
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33
Q

Neurulation

A

The process of creating the nervous system once the 3 germ layers formed.
- The notochord contains neural folds which surrounds the neural groove. This creates the neural tube.
- The neural tube becomes the central nervous system while the the cells at the tip of the neural tube contains neural crest cells which turns into the peripheral nervous system.

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34
Q

Tetrogens

A

Substances that harm the development of the fetus.
Tetrogens can include: alcohol, some prescription drugs, viruses, environmental factors, diabetes, folic acid deficiency.

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35
Q

Cell specialization includes determination and differentiation. What are these?

A
  • Determination- When the cell becomes set ( “ determined”) to a certain cell lineage. This happens when cells responds to morphegans. In order to responds to morphegans the cell must have competency.
  • Differentiation is the selective transcription that leads to a specific cell.
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36
Q

What are stem cells? Describe the following stem cell classes.
- Totipotent
- Pluripotent
- Multipotent
- Unipotent

A

Stem cells are cells that can become other classes of cells.
- Totipotent - cell can differentiate into ANY type of cell in the body. Any of the 3 germ layers and placental cells.
- Pluripotent- cell can become any cell type of any of the 3 germ layers.
- Multipotent - cell can become any cell of one of the 3 germ layers.
- Unipotent- cell can become only one specific type of cell.

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37
Q

Cells that communicate to other cells are refered to as what. What are the recieving cells called?

A

Inducers are the cells that sends the signal while responders receive the signal.

  • Reciprocal induction is when two cells induce differentiation in each other.
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38
Q

Autocrine
Paracrine
Juxtacrine
Endocrine

A

Autocrine- Signal that acts on the same cell that released the signal.

Paracrine- signal travels a short distance to reach responder. Signal travels short distance.

Juxtacrine - signal acts acts on adjacent cells

Endocrine - signals travel through bloodstream. Signal moves long distance.

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39
Q

Apoptosis

A

Programmed cell death that’s initiated by formed apoptotic blebs that forms around the cell and allows it to be absorbed and digested.

40
Q

Regenerative capacity v. Senescence

A

Regenerative capacity is the ability to regrow parts of their body.

Senescence is the reduction of telomeres after sequential steps of mitosis. Reason behind aging.

41
Q

Nutrient, gas exchange, and waste exchange happens where?

A

The placenta. HbF ( Fetal hemoglobin) which has a higher affinity for oxygen than adult hemoglobin.

42
Q

Where does pathogens and antibodies be exchanged with the fetus?

A

The placenta.

The placenta also serves endocrine functions releasing estrogen, progesteron, and Hcg ( Human chorionic gonadotropin)

43
Q

Umbilical veins carry what type of blood and umbilical arteries carry what type of blood?

A

Umbilical veins carry oxygenated blood to placenta while umbilical arteries carry deoxygenated blood to placenta.

44
Q

What are the shunts in the fetus?

A

They serve to bypass the lungs and the liver.

  • Foramen ovale- connects right atrium to left atrium to bypass lungs.
  • Ductus arteriosus- connects pulmonary artery to aorta to bypass lungs.
  • Ductus venous- connects umbelical vein to inferior vena cava to bypass liver.
45
Q

What happens during the first, second, and third trimesters?

A

First trimester the organs develop; second trimester growth accelerates and the face become more human like, and there’s movement; third trimester is when the brain develops, rapid growth continues and there is transfer of antibodies from mom to fetus.

46
Q

What happens when gametes from each parent meet?

A

The sperm meets the oocyte which are both haploid. They come together to form a diploid zygote with genes alleles for genes coming from each parent.

47
Q

Describe the components of the male reproductive system.
- Testes

  • Scrotum
  • Epididymis
  • Ductus vas deferentia
  • Seminal glands
  • Prostate gland
  • Bulbourethral ( Cowper’s) gland
  • Urethra
  • Penis
A
  • Testes - sites of spermatogenesis and sex hormone production.
  • Scrotum -holds to testes at a temperature 2-4 degrees Celsius below the body temperature which is needed for spermatogenesis.
  • Epididymis - where sperm cells go to mature and become motile. Store there until release.
  • Ductus vas deferentia - transports the sperm from the epididymis to the urethra.
  • Seminal vesicles (seminal glands) - creates fructose and other substances that the sperm uses to power their flagella.
  • Prostate gland - secretes prostatic fluid which prevents sperm coagulation in the vagina.
  • Bulbourethral (Cowper’s) gland - secretes an alkaline, mucous fluid that lubricates tip of penis. Gives the sperm a slight alkaline to protect the sperm in the acidic environment of the vagina.
  • Urethra - participates in both excretory and reproductive system (semen and urine).
  • Penis - where semen exists (mix of sperm and seminal fluid).
48
Q

Seminiferous tubules v. Sertoli cells

A

Semiferous tubules is where spermatogenesis occurs. Sertoli cells serve to nourish them as they grow.

49
Q

Leydig cells

A

Secretes testosterone in response to ACTH. Testosterone is required for spermatogenesis.

50
Q

Seminal fluid

A

Where sperm resides and serves to support the nutrition and movement of the sperm.

51
Q

Early and late spermatids

A

Early spermatids are not motile. When early spermatids turn to late spermatids you have the development of the flagella and cleaving off of additional cytoplasm before they become spermatozoa.

52
Q

What are the parts of the sperm?

A
  • Head - contains the acrosome and the nucleus. The acrosome serves to break through the corona radiata and corona pellucida of the oocyte.
  • Midpiece - contains mitochondria which produces ATP for sperm movement.
  • Tail - made of flagella. Serves to move the sperm out of the urethra and through the female reproductive tract.
53
Q

How does the SRY gene develops male characteristics?

A

When the SRY gene is expressed the sertoli cells secrete AMH (anti- mullerian hormone) which inhibits the mullerian ducts from developing. When they are inhibited this causes the release of androgens which causes the expression of woffian ducts which develops into male structures.

54
Q

HPG axis

A

Hypothalamic pituitary gonadotropic axis.

The axis that causes the release of sex hormones. Hormones are released on the onset of puberty.

55
Q

Role of FSH and LH in male reproductive system?

A

FSH stimulates Sertoli cells which serves to nourish sperm, and LH stimulates Leydig cells which secretes testosterone.

56
Q

The male reproductive system exerts negative feedback on the HPG axis by which two ways?

A

When testosterone levels are too high. It exerts negative feedback on hypothalamus and a. pituitary.

Sertoli cells can secrete inhibin which acts on anterior pituitary and stop secretion and FSH and LH stopping nourishment of sperm cells.

57
Q

Describe the following components of the female reproductive system.

  • Ovaries
  • Fallopian tubes
  • Uterus
  • Cervix
  • vagina
  • vulva
  • mammary glands
A
  • ovaries - site of oogenesis, secretes sex hormones (estrogen and progesterone).
  • Fallopian tubes - connects the ovaries to the uterus. Contains hair-like projections that propel the oocyte in the tube.
  • Uterus -protects and nourishes embryo and developing fetus, contains two linings.
    Inner lining is the endometrium which changes thickness at different stages along the mensturation cycle.

They myometrium is a smooth muscle layer that contracts during menstruation and childbirth.

  • Cervix - inferior part of the uterus, connects the uterus to the vagina.
  • Vagina - releases fluids, receives penis, and is the final segment of the birth canal.

-vulva (female external genetalia) - contains two folds the labia majora and labia minora which protects the opening of the vagina. When the clitoris is stimulated it causes changes in the vagina that increases reproductive success.

  • Mammary glands - located in chest, they become completely developed during puberty and develops milk ( lactation) for breastfeeding.
58
Q

What cells in the ovaries is the site of oogenesis?

A

ovarian follicles, located in the ovaries.

59
Q

What cell type does follicular cells develop into and what is their function?

A

They develop into granulosa cells which secretes sex hormones to aid in the developing oocyte.

60
Q

Which ducts are responsible for female characteristics?

A

Mullerian ducts, since they don’t have the SRY gene. This causes the wolffian ducts to degenerate due to lack or testosterone.

61
Q

Which sex hormones are released once puberty is initiated?

A

Estrogen and progesterone in females and testosterone in males. Causes formation of secondary sex characteristics.

62
Q

Ovarian cycle v. Menstrual cycle

A

Ovarian cycle - the cycle involved in making oocytes.

Menstruation cycle - the cycle that’s involved in preparing the uterus for pregnancy.

63
Q

Describe the follicular phase of the ovarian cycle

A

There is low levels of estrogen and progesterone and high levels of FSH and LH which stimulates development of follicular cells which secretes estrogen exhibiting negative feedback on the anterior pituitary.

Only one follicle survives and secretes inhibin, serving to inhibit FSH release from a. pituitary. This inhibits development of more follicles.

Once the dominating follicle matures it stops secreting inhibin and estrogen switches to positive feedback causing higher levels of LH than FSH.

64
Q

Describe the process of ovulation

A

The follicular cells rupture causing a release of oocytes into the abdominal cavity.

65
Q

Describe the luteal phase

A

Rupture follicular cells turn into the corpus luteum which secretes progesterone. Progesterone exerts negative feedback on the HPG axis to prevent maturation of follicle.

If oocyte is fertilized (pregnancy) corpus luteum keeps secreting progesterone to keep FSH and LH levels low.

66
Q

Describe the concurrent ovarian and menstrual cycles

A

Menstrual cycle (1-4 days) - If fertilization doesn’t occur menstruation begins. During menses the endometrial layer flows out of uterus and vagina. Ovarian follicles are stimulated to grow to begin a new cycle.

Proliferative phase (5- 14 days) - endometrial layer continues to grow to prepare for embryo implantation.

Secretive phase (15- 28 days) - Increased release of estrogen and progesterone creates suitable environment for a growing embryo.

67
Q

How does the oocyte move from the ovaries into the fallopian tube during ovulation?

A

Through projections called fimbriae which are located in the fallopian tubes.

68
Q

What changes does the female reproductive system makes to the sperm once in?

A

Increases sperm’s membrane permeability and increase in flagellar movement.

The sperm moves past the corona radiata and binds to glycoproteins on the zona pellucida.

69
Q

What’s the role of the acrosome in sperm?

A

It releases hydrolytic enzymes to break through the zona pellucida causing the release of the sperm’s mitochondria, nucleus, and centrioles.

70
Q

What happens once fusion occurs of the sperm and oocyte?

A

The cortical reaction

Intracellular calcium is released from the oocyte through their cortical granules to fuse with membrane and release hydrolytic enzymes preventing more sperm from fertilizing oocyte.

71
Q

What happens after sperm penetrates the oocyte?

A

The oocyte undergoes meiosis 2 and the pronucleus of both the ovum and sperm come together to form a diploid zygote.

72
Q

Cleavage

A

The rapid mitotic division of newly formed zygote.

The division creates multiple cells called blastomeres which develops into the morula.

73
Q

The morula divides into what? What are the layers of this new structure?

A
  • The morula divides into the blastocyst.
  • The blastocyst contains a fluid filled center called the blastocoel with two cell layers. The inner cell mass and trophoblast (which develops into embryonic tissues such as the placenta).
74
Q

What happens once the oocyte turns into a blastocyst?

A

It moves from the fallopian tube to the uterus where it implants and forms the placenta which will support the developing embryo.

75
Q

Which cells are in charge of implantation of the blastocyst into the uterus?

A

Trophoblast cells.

Once implantation occurs it secretes HCG ( human chorionic gonadotropin) which maintains the endometrial layer until the placenta develops and take over.

76
Q

Where is the chorion located?

A

It’s part of the placenta and contains chorionic villi.

77
Q

What structures does the inner cell mass of the blastocyst turn into?

A

They develop into the yolk sac, allantois, and amnion.

78
Q

What happens after the blastocyst implants into the uterus?

A

The process of organogenesis starts which is the develop of developing embryonic tissues and organs.

This includes germ layer development and neurulation.

79
Q

What are the cells of the inner cell mass and what do they turn into?

A

They contain hypoblast cells and epiblast cells.

  • Epiblast cells create the primitive streak which separate the embryo into posterior and anterior axes.

They divide into the three germ layers.

Cells that form internal structures moves inside while cells that form the skin and NS moves to the outside.

80
Q

What organs come from the three germ layers?

A

Ectoderm - skin and NS

Mesoderm - muscle, bone, and other connective tissues

Endoderm - internal organs and digestive tract.

81
Q

What happens after gastrulation?

A

Neurulation in which the notochord sends a signal to stimulate the development of neural tissues. This gives rise to organs.

82
Q

Neurula develops into which three cell types.

A

Neural crest cells, neural plate cells, epidermal cells.

83
Q

Symmetrical stem cell division v. Asymmetrical stem cell division

A

Symmetrical stem cell division is when the stem cell divides into two cells of a specific cell type or two of the same stem cells (increasing stem cell population).

Asymmetrical stem cell division is when one stem cell is created and one specific cell type is created from stem cell.

84
Q

Cell specification v. Cell determination

A

The cell type a stem cell is capable of turning into. Can change if we give it different signals.

Cell determination is when the stem cell becomes set on becoming a certain cell type. Doesn’t change even when we put it in different conditions.

85
Q

X- inactivation

A

Silencing of female X chromosome since they have 2x as many X chromosomes as men. Happens through the XIST gene. Happens to a random X chromosome.

Once inactivated it’s referred to as a barr body.

86
Q

What are the cells called that send signals for cell division or cell differentiation?

A

The cells that send the signal is called the inducers and the receiving cells must be competent in order to receive the signal.

The messages are called morphogens which exist as a gradient.

Messages can reciprocal meaning they induce each other.

87
Q

Lateral inhibition

A

When in adjacent cells one cell causes the other to differentiate while that cell remains the same. Happens through juxtracrine signaling.

88
Q

What are the two periods of gestation (pregnancy)?

A

The embryonic period - starts with the formation of the zygote until the beginning stages of organogenesis.

The fetal period - starts from the beginning of the organogenesis until birth and is characterized by the growth of organs.

89
Q

Describe the trimesters of gestation.

A
  1. First trimester - includes formation of zygote (fertilization), implantation, the embryonic period, and a few weeks of the fetal period.
  2. Second trimester - the placenta develops and is fully functioning it supports the fetus and secretes pregnancy hormones.
  3. Third trimester
90
Q

Describe how fetus and mother exchange nutrients and wastes?

A

Before the fetal circulatory system develops oxygen, nutrients, CO2, and wastes are exchanged between mother and fetus using the mother’s circular system.

Once the fetal circulatory system develops exchange happens between the mother and fetal circulatory system at the placenta via the umbilical cord which is connected to fetus at the umbilicus.

91
Q

Describe the process of parturition)?

A

Pressure on the cervix causes the release of oxytocin which in turns causes the release of prostaglandins in the uterine myometrium causing contractions.

Oxytocin exerts positive feedback until no pressure is on the cervix (birth).

92
Q

What are the three stages of labor?

A
  1. Dilation of the cervix - the rupture of the amniotic sac causing release of amniotic fluid.
  2. Expulsion - delivery of the baby through the cervix.
  3. Delivery of the placenta- placenta is released from the uterine wall.
93
Q

Describe the hormonal process of breast feeding?

A

When the baby latches onto the nipple it causes release of prolactin which stimulates production of milk and oxytocin which lets down the milk.

This is a positive feedback mechanism.

94
Q

Tissue regneration

A

Early in life tissue injury can be regenerated but as you age this process stops, that’s called senescence.

95
Q

What happens when tissue injury cannot be regenerated via tissue regeneration?

A

Repair happens which is the process of creating scar tissue in the damaged area.

96
Q

Senescence

A

Decrease in the proliferation of cells.

Caused by telomere shortening, genomic instability, or mitochondrial dysfunction.

Associated with the process of aging.

MCAT Biology and Biochemistry (19 decks)

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