MIDTERMS LEC NCM 107 lecture # 1 (3) The sperm fuses with the egg cell membrane, causing the Zona Pellucida to
become impenetrable to other sperm
PREGNANCY AND PRENATAL CARE (4) The tail separates from the sperm head, and the male pronucleus enlarges and
travels to the female pronucleus in the center of the cell
I. FERTILIZATION
- the union of the sperm and the mature ovum in the outer third or outer half of the FERTILIZATION IS NEVER A CERTAIN OCCURRENCE BECAUSE IT
fallopian tubes DEPENDS ON AT LEAST 3 SEPARATE FACTORS:
- Also, referred to as conception, impregnation, and fecundation 1. Equal maturation of both sperm and ovum
2. The ability of the sperm to reach the ovum
OVUM AND SPERM 3. The ability of the sperm to penetrate the Zona Pellucida and cell membrane and
• Ovum fertile for 12-24 hrs achieve fertilization
• Sperm can survive up to 72hrs (most healthy at 24hrs)
• Sperm must undergo capacitation and acrosomal reaction
- the process consists of changes in the plasma membrane of the sperm II. IMPLANTATION
head, which reveal the sperm-binding receptor sites (1) Immediately after fertilization, the fertilized ovum or zygote stays in the
- the final process that sperm must undergo to be ready for fertilization fallopian tube for days, during which time rapid cell division (mitosis) is taking
• Hyaluronidase - a proteolytic enzyme place
- released by the spermatozoa and acts to dissolve the layer of cells (2) The developing cells are now called Blastomere and when there are already
protecting the ovum (Corona Radiata) about 16 blastomeres, it is now termed a Morula
(3) In this Morula form, it will start to travel by ciliary action and peristaltic
* Corona Radiata - supply vital proteins to the cell contractions of the fallopian tube
* Zona Pellucida — Protective later of the ovum (1 sperm can enter) (4) When there is already a cavity formed in the morula, it is now called a Blastocyst
(5) Fingerlike projections called Trophoblasts form around the blastocyst and these
GENERAL CONSIDERATIONS trophoblasts are the ones which will implant high on the anterior or posterior
1. Normal amount of semen per ejaculation (3-5 cc/ 1tspn) surface of the uterus
2. Number if sperms in an ejaculate ( 120-150 million/cc) (6) Thus, implantation or Nidation takes place about a week after fertilization
3. Mature ovum is capable of fertilizing even for 3-4 days after ejaculation.
4. Normal life span of sperms (7 days)
5. Sperms, once deposited in the vagina will generally reach the cervix within 90s
after disposition.
DURING FERTILIZATION
(1) Ovum captured by fimbriae to the fallopian tube
(2) Semen ejaculate of millions of spermatozoa
(3) Decrease in Cervical Mucus viscosity facilitates entry of spermatozoa
(4) Spermatozoa moves by Flagella and uterine contractions until it reaches the
ovum
FERTILIZATION OF A HUMAN EGG
(1) The sperm release enzymes that help disperse the Corona Radiata and bind to the
Zone Pellucida
(2) The outer sperm head later is sloughed off, exposing enzymes that digest a path
through the Zona Pellucida
, GENERAL CONSIDERATIONS
(1) Once implantation has taken place, the uterine endothelium is now termed - Purposes:
Decidua 1. Protection - shields the fetus against blows or pressure on the mothers abdomen;
• Decidua Basalis - part of endometrium under the embryo; trophoblast establishing against sudden changes in temp, liquid changes temp more slowly than air; and from
communication with maternal blood vessels infection
• Decidua Capsularis - stretches/encapsulates trophoblasts 2. Diagnosis- as in Amniogentesis; meconium stained amniotic fluid means fetal
• Decidua Hera - portion of the uterine lining distress
(2) Occasionally, a small amount of vaginal spotting appears with implantation 3. Aids in descent of the fetus during active labor
because capillaries are ruptured by the implanting trophoblasts (do nit mistake for
LMP)
Second Fetal Membrane:
Chorion - together with the decidua basalis, gives rise to the placenta
III. OUTLINE OF TROPHOBLAST DIFFERENTIATIONS -Placenta :
I. Cytotrophoblast - inner layer - 2 presentations
II. Syncytiotrophoblast - outer layer containing fingerlike projections called - Duncan- Dirty
Chorionic Villi which differentiate into: - bloody side of the placenta
- faced the uterus of the mother
a.) Langhan’s layer - believed to protect the fetus against Treponema Pallidum - Schumltze - shiny
(etiologic agent of spyhilis); present only during the 2nd trimester of pregnancy. - fetal surface of the placenta
b.) - 15-20 cotyledons
Syncyial layer - gives rise to the fetal membrane: - Starts to form at 8th week gestation
- Purposes:
First fetal membrane: 1. Respiratory system- exchange of gases takes place in the placenta not in the fetal
Amnion - inner membrane which gives rise to: lungs
2. Renal system- waste products are being excreted through the placenta (it is the
• Umbilical Cord/ Funis mothers liver which detoxified the fetal waste products)
- contains 2 arteries and 1 vein which are supported by the Wharton’s Jelly 3. Gastrointestinal system- nutrients pass to the fetus via the placenta by diffusion
• Amniotic Fluid through the placental tissues
- clear, Albuminous fluid in the which the baby floats 4. Circulary systems - feto-placenta circulation is established by selective osmosis
- Begins to form at 11-15 weeks gestation 5. Endocrine systems- it produces the ff important hormones (before 8 wks gestation,
- Approx water in specific gravity (1.007-1.025) and is neutral to slightly alkaline the corpus luteum is the one producing these hormones):
(pH 7.0-7.25)
- Near term is clear, colorless, containing kittle white specks of Vernix Caseosa and • Human Chorionic Gonadrotropin (HCG)
other solid particles - orders the corpus luteum to keep on producing estrogen and
- Produced at a rate of 500ml in 24hrs and fetus swallows it an equally rapid rate progesterone (that is why menstruation does not occur during
- By the 4th Lunar Month, urine is added to the amount of Amniotic fluid pregnancy)
- Derived chiefly from maternal serum and fetal urine • Human placental lactogen (HPL) -
- POLYHYDRAMNIOS (more than 1500ml amniotic fluid) stems from the promote growth of mammary glands necessary for lactation
inability of the fetus to swallow fluid rapidly, as in tracheoesophageal fistula • Estrogen and Progesterone
- OLIGOHYDRAMNIOS (less than 500ml) is dude to the inability of the kidney to 6. Protective barrier
add urine to the amniotic fluid m, as in Congenital renal anomaly
- Also known as bag of water (bow)
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