A&P lecture 9 wk11 Pregnancy

winniesmith1's version from 2017-05-20 18:44

Section 1

Question Answer
definition of developmentGradual modification of anatomical structures and physiological characteristics from fertilization to maturity
Where does development beginat fertilization, or conception
What does development involve1. Division and differentiation of cells 2. Changes that produce and modify anatomical structures
What is differentiationCreation of different types of cells required in development
When does differentiation occurthrough selective changes in genetic activity: as development proceeds, some genes are turned off, others are turned on
What is inductionCells release chemical substances that affect differentiation of other embryonic cells. Can control highly complex processes.
What are the 4 stages of developmentEmbryological, foetal, prenatal and postnatal
What is embryological developmentevents that occur in the first 2 months after fertilization
What is foetal developmentbegins at 9 weeks of pregnancy and continues until birth
What is prenatal developmentEmbryological and foetal development
What is postnatal developmentbegins at birth and continues to maturity when the aging process begins
What is inheritance Transfer of genetically determined characteristics from generation to generation
What is geneticsStudy of mechanisms responsible for inheritance

Section 2

Question Answer
What is the fetilizationFusion of 2 haploid gametes, each containing 23 chromosomes. Producing zygote containing 46
Describe function of spermatozoon-Delivers paternal chromosomes to fertilization site. -Travels relatively large distance, taking 30 mins – 2 hours. Small, efficient, and highly streamlined. -Of 200 million introduced into the vagina, 10,000 enter the uterine tube, ~100 reach the secondary oocyte
Describe function of the female gamete- secondary oocyte.Provides: cellular organelles, nourishment, and genetic programming necessary to support development of embryo for a week. Oocyte becomes fully mature only after fertilisation. Must travel a few centimeters.
How long can the female egg surviveonly 24 hours after ovulation
Compare the diameter of secondary oocyte to spermDiameter of secondary oocyte is >2 times the length of a spermatozoon. Volume ratio = 2000 to 1
When does fertilization usually occur uterine tube within a day after ovulation
What must happen to the spermatozoa before it can fertilize the secondary oovyteCapacitation- refers to the physiological changes spermatozoa must undergo in order to have the ability to penetrate and fertilize an egg.
-contact with secretions of seminal vesicles.
-exposure to conditions in female reproductive tract.

Section 3

Question Answer
What is the corona radiatalayer of follicular cells surrounding the oocyte
what does corona radiata do Protects the oocyte during and following ovulation
What must the sperm penetratefirst the corona radiata and then the zona pellucia.
how do the sperm penetrate eggAcrosomal cap of sperm release hyaluronidase and acrosin
The oocyte is suspended in what phasemetaphase of meiosis II
What is hyaluronidase enzyme which breaks down bonds between adjacent follicle cells, which allows sperm to reach egg.
How do sperm break down radiata/zona pellucidaDozens of sperm cells must release hyaluronidase before an opening forms. Then releases acrosin.
What is acrosinsecond enzyme required for spermatozoon to reach oocyte
When/how does fertilization occurA single sperm will accomplish fertilization and activate the oocyte. It binds to receptors in the zona pellucida. Acrosomal cap ruptures, releasing hyaluronidase and acrosin, which digests a path through the zona pellucida to the oocyte membrane.

Section 4

Question Answer
When does oocyte activation occur when the cell membranes of the sperm and oocyte fuse
What happens once the oocyte is activated Oocyte completes meiosis II, becomes mature ovum. Oocyte activation leads to sudden changes in its metabolism. Vesicles inferior to the cell membrane release enzymes which prevent entry of additional sperm.
What is a female pronucleus nuclear material remaining in ovum after oocyte activation
What is a male pronucleusSwollen nucleus of spermatozoon, migrates to centre of cell
What is amphimixis -Fusion of female pronucleus and male pronucleus -Moment of conception, fertilization complete -Cell becomes a zygote with 46 chromosomes

Section 5

Question Answer
What is gestationTime spent in prenatal development
What is the time spent in gestationThe average length of human gestation is 280 days, or 40 weeks, from the first day of the woman's last menstrual period. Actual gestation is ~266 days, 38 weeks. Consists of 3 integrated trimesters, each 3 months long.
What happens throughout gestationprenatal development, a single cell forms into a 3-4 kg (~7 lb) infant
When is gestation period recorded to startfrom last day of period
What mammal has the shortest gestation periodPossom. 12-13 days
What mammal has the longest gestation periodAfrican Elephant. 20 months (645 days)

Section 6

Question Answer
What happens in the 1st trimester-Period of embryological and early foetal development. -Rudiments of all major organ systems appear.
What happens in 2nd trimesterDominated by the development of organs and organ systems. Body shape and proportions change, by end foetus looks distinctively human
What happens in 3rd trimesterRapid foetal growth and deposition of adipose tissue. Most major organ systems are fully functional

Section 7

Question Answer
Describe the 1st trimester Many complex and vital developmental events occur in the first trimester. Most dangerous period of prenatal life – only ~40% of conceptions produce embryos that survive this period
What are the key processes which occur during 1st T-Cleavage and blastocyst formation -Implantation -Placentation -Embryogenesis
What is cleavage - Series of cell divisions, production of daughter cells
What happens in cleavage and blastocyst formation stage (pg28)Sequence of cell divisions begin immediately after fertilization. Zygote becomes a pre-embryo, which develops into multicellular blastocyst (by day 6). Ends when blastocyst contacts uterine wall (by day 8).
How is a blastocyst formedby blastomeres (identical cells produced by cleavage divisions)
Describe a blastocystHollow ball with an inner cavity, known as blastocoele. Blastocyst surrounded by the trophoblast – outer layer of cells responsible for providing nutrients to developing embryo. Inner cell mass – will later form embryo.
What happens in hatchingshredding of zona pellucida

Section 8

Question Answer
What happens in implantation(basic overview)Blastocyst adheres to uterine lining. Trophoblast cells divide rapidly, creating several layers. Cells closest to interior of blastocyst form a layer - cellular trophoblast.
(USE SLIDES-pg29-32- Add days) When does implantation occur 7 days after fertilisation
What stages happen in implantation (complex)(days 6-9) Outer cell layer forms the syncytial trophoblast (day 5) Syncytial trophoblast erodes path through uterine epithelium, where it continues to enlarge. Erosion of uterine gland cells releases nutrients. Nutrients absorbed by trophoblast and spread by diffusion to inner cell mass.
What happens around day 10 Extensions of syncytial trophoblast surround endometrial capillaries. Trophoblastic channels form, lacunae, which carry maternal blood. Finger like villi extend from the trophoblast into endometrium. Villi increase in size and complexity until day 21.
What happens near the end of implantation Inner cell mass separates from trophoblast. Separation enlarges forming the amniotic cavity. Cells of the inner cell mass organised into an oval sheet, 2 cell layers thick.
What happens by day 12 a third layer of cells begin forming, through the process of gastrulation. Cells exposed to the amniotic cavity move towards the primitive streak and migrate between the 2 existing layers
What does gastrulation lead to 3 distinct embryonic cell layers – primary germ layers: Ectoderm, Mesoderm, Endoderm.
What do the 3 cell layers form an oval sheet embryonic disc. Forms the body of the embryo. Remainder of blastocyst forms extraembryonic membranes.

Section 9

Question Answer
Formation of extraembryonic membranes. name the 4 -yolk sac -amnion -allantois -chorion
What is the function of the yolk sacBegins as layer of cells spread out around outer edges of blastocoele to form complete pouch. Important site of blood cell formation.
What is the function of the amnionEctodermal layer enlarges and cells spread over inner surface. Mesodermal cells create outer layer. Continues to enlarge through development. Encloses amniotic fluid that surrounds and cushions developing embryo and foetus.
What is the function of the allantoisSac of endoderm and mesoderm. Base later gives rise to urinary bladder.
What is the function of the chorion Combination of mesoderm and trophoblast. Blood vessels develop within esoderm. Rapid-transit system for nutrients that links embryo with trophoblast. First step in creation of functional placenta.
Week 2
Week 3
Week 4

Section 10

Question Answer
What is the placentaTemporary structure in uterine wall that provides a site for diffusion between foetal and maternal circulatory systems
How does the placenta formFormed when blood vessels form in chorion around the periphery of the blastocyst. Chorionic villi form in week 3 which contact maternal tissues. This creates intricate network within endometrium carrying maternal blood. Embryonic blood vessels develop in each villus and circulation begins early in week 3 when the heart starts beating.
week 5
week 10
What happens in the placentaDeoxygenated blood flows from the embryo/foetus to the placenta through paired umbilical arteries. Oxygenated blood returns to the embryo/foetus in a single umbilical vein. Chorionic villi provide surface area for exchange of gases, nutrients and wastes
What are the placenta hormones Synthesized by syncytial trophoblast, released into maternal bloodstream: Human chorionic gonadotropin, Human placental lactogen, Placental prolactin, Relaxin, Progesterone, Estrogens.

Section 11

Question Answer
What is embryogenesisProcess of embryo formation
What happens in embryogenesis-Body of embryo begins to separate from embryonic disc. -Body of embryo and internal organs start to form. -Folding, differential growth of embryonic disc produce bulge that projects into amniotic cavity: projections are head fold and tail fold.
What do the events in the first trimester establish a basis for organogenesis – process of organ formation
What has happened by end of 1st trimesterall organ systems have formed by the end of the first trimester.

Section 12

Question Answer
What happens during the 2nd T foetus grows faster than surrounding placenta. By end of second trimester, the foetus will weigh 1.4 lbs (0.6 kg)
What happens during 3rd TDuring third trimester, the basic components of all organ systems appear. Most become ready to perform their normal functions. Rate of growth starts to decrease.the largest weight gains occur in this trimester
What is the weight of foetus in 3rd T5.7 lbs (2.6 kg), reaching a full term weight of ~7 lbs (3.2 kg). Fetus and enlarged uterus displace many of mother’s abdominal organs
Size/composition of uterus at end of gestationa typical uterus will have grown from 7.5 cm long to 30 cm. It will have gone from 60g in weight to 1100g. It will likely contain 5 litres of fluid having a total weight of 10 kg (22 lbs) (including the foetus). This expansion occurs through the enlargement of existing cells, mainly smooth muscle cells.

Section 13

Question Answer
Maternal adaptations include increases in -respiratory rate -tidal volume -blood volume -nutrient and vitamin intake -glomerular filtration rate -uterus and mammary glands increase in size
Factors involved in initiating and sustaining labour and deliverypg61
How are contractions brought amouthby smooth muscle in uterus
What is the goal of labourparturition – the forcible expulsion of the foetus from the uterus
Describe labour contractions -Begin near the top of the uterus and sweep in a wave towards the cervix. -Are strong, occur at regular intervals, increase in force and frequency. -Change position of foetus, move it towards cervical canal
What are the stage of labour1.Dilation stage 2.Expulsion stage 3.Placental stage
What happens in dilation stage -Begins with onset of true labour -Cervix dilates -Foetus begins to shift toward cervical canal -Highly variable in length, typically lasts over 8 hours -Frequency of contractions steadily increase -Amniochorionic membrane ruptures (water breaks)
What happens in expulsion stage -Begins as cervix completes dilation -Contractions reach maximum intensity -Continues until foetus has emerged from vagina, typically less than 2 hours -Delivery - arrival of newborn infant into outside world
What happens in placental stage -Muscle tension builds in walls of partially empty uterus -Tears connections between endometrium and placenta -Ends within hour of delivery with ejection of placenta, or afterbirth -Accompanied by a loss of blood