EARLY_EMBRYOLOGY

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soren101
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29179
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EARLY_EMBRYOLOGY
Updated:
2010-08-07 21:01:59
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embryology
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early embryology for med school
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  1. DEFINE THE EMBRYONIC PERIOD AND LIST ITS STAGES
    EXTENDS FROM FERTILIZATION (DAY 1) TO END OF 8TH WEEK (DAY 56)

    -ZYGOTE: CELL THAT RESULTS FROM UNION OF EGG AND SPERM

    -EMBRYO: EARLY STAGES IN UTERO (DAY 1 - 56)

    -CONCEPTUS: "PRODUCTS OF CONCEPTION", EMBRYO AND ASSOCIATED MEMBRANES (EMBRYO, EMBRYONIC PART OF PLACENTA, AMNION, CHORIONIC SAC, YOLK SAC)
  2. DEFINE THE FETAL PERIOD
    EXTENDS FROM 9TH WEEK (DAY 57) TO BIRTH; PRIMARILY PERIOD OF DIFFERENTIATION AND GROWTH OF TISSUES AND ORGANS
  3. WHY IS EXPOSURE TO TERATOGENETIC AGENTS MOST HARMFUL DURING EMBRYONIC PERIOD?
    CRITICAL PERIOD FOR SENSITIVITY TO STRUCTURAL TERATOGENESIS

    3RD THROUGH 8TH POST-FERTILIZATION WEEK IS THE PERIOD DURING WHICH ALL THE MAJOR ORGAN SYSTEMS OF THE BODY ARE BEING FORMED.
  4. LENGTH OF GESTATION IN DAYS, WEEKS, MONTHS FROM BOTH TIME OF FERTILIZATION AND LAST NORMAL MENSTRUAL PERIOD (LNMP)
    • DAYS WEEKS MONTHS
    • FERTILIZATION: 266 38 8.75

    LNMP: 280 40 9.25
  5. WHAT DOES MEIOSIS ACHIEVE RELATIVE TO MITOSIS (3)
    1) REDUCTION TO HAPLOID NUMBER GAMETES

    2) RANDOM ASSORTMENT OF MATERNAL & PATERNAL CHROMOSOMES BETWEEN GAMETES

    3) CROSSING OVER ALLOWING RECOMBINATION OF GENETIC MATERIAL
  6. LIST STAGES OF POSTNATAL DEVELOPMENT AND TIMEPERIODS WHERE APPROPRIATE (4)
    1) NEONATE -- ONE MONTH TO 1 YEAR

    2) INFANT -- 1-YEAR-OLD OR YOUNGER

    3) PUBERTY

    4) MENARCHE
  7. WHAT ARE OOGONIA AND WHAT DO THEY FORM?
    FEMALE GERM CELLS THAT PROLIFERATE BY MITOSIS DURING EARLY FETAL LIFE

    FORM PRIMARY OOCYTES BEFORE BIRTH
  8. DEFINE PRENATAL DEVELOPMENT OF OOCYTE (3)
    1) OOGONIA ENLARGE TO FORM PRIMARY OOCYTE

    2) PRIMARY OOCYTE BEGIN FIRST MEIOTIC DIVISION BEFORE BIRTH; PROPHASE IS NOT COMPLETED 'TIL AFTER PUBERTY, ARESTED DUE TO MATURATION INHIBITOR RELEASED BY FOLLICLE CELLS

    3) PRIMARY OOCYTE + SUROUNDING LAYER OF FLATTENED EPITHELIAL FOLLICULAR CELLS = PRIMORDIAL FOLLICLE
  9. POSTNATAL MATURATION OF OOCYTES AND OVULATION (4)
    1) ZONA PELLUCIDA FORMS BETWEEN PRIMARY FOLLICLE CELLS AND OOCYTE TO MATURE 15-20 PRIMARY OOCYTES EACH MONTH

    2) ONE PRIMARY OOCYTE COMPLETES 1ST MEIOTIC DIVISION JUST BEFORE OVULATION, FORMING SECONDARY OOCYTE AND 1ST POLAR BODY

    3) SECONDARY OOCYTE BEGINS 2ND MEIOTIC DIVISION, BUT STOPS IN METAPHASE

    4) 2ND MEIOTIC DIVISION COMPLETED WHEN SPERM ENTERS SECONDARY OOCYTE, FORMING A FERTILIZED OOCYTE (ZYGOTE) AND 2ND POLAR BODY
  10. ATRESIA
    NORMAL PROCESS OF PROGRAMMED CELL DEATH IN PRIMARY OOCYTES AND PRIMARY FOLLICLES
  11. OVARIAN CYCLE (6)
    1) FSH STIMULATES 15-20 PRIMARY FOLLICLES TO GROW

    2) 1 REACHES MATURITY AND OTHERS UNDERGO ATRESIA

    3) THECAL CELLS SURROUND AND PROMOTE GROWTH OF BLOOD VESSLES

    4) FOLLICLE CELLS PROLIFERATE AND PRODUCE FLUID TO FORM CAVITY (ANTRUM); NOW CALLED SECONDARY FOLLICLE

    5) PRIMARY OOCYTE IN SECONDARY FOLLICLE SURROUNDED BY CUMULUS OOPHORUS (FOLLICLE CELLS)

    6) FOLLICLES PRODUCE ESTROGEN
  12. OVULATION CYCLE (7)
    1) SURGE OF LH CAUSES PRIMARY OOCYTE TO COMPLETE 1ST MEIOTIC DIVISION

    2) INTRAFOLLICULAR PRESSURE, SMOOTH MUSCLE CONTRACTION IN THECA, AND ENZYMATIC DIGESTION CAUSES RUPTURE OF SECONDARY FOLLICLE

    3) SECONDARY OOCYTE AND 1ST POLAR BODY (SURROUNDED BY ZONA PELLUCIDA AND CUMULUS OOPHORUS) ARE EXPELLED

    4) CUMULUS OOPHORUS REARRANGES TO FORM CORONA RADIATA

    5) WALLS OF FOLLICLE AND THECA FORM CORPUS LUTEUM, WHICH SECRETES PROGESTERONE & ESTROGEN

    6) PROGESTERONE AND ESTROGEN PREPARE ENDOMETRIUM OF UTERUS

    7) IF NO PREGNANCY THEN MENSTRUAL CYCLE OCCURS
  13. OOCYTE TRANSPORT AND VIABILITY (4)
    1) DURING OVULATION, FIMBRIAE OF UTERINE TUBE MOVE OVER OVARY

    2) CILIA OF MUCOSAL CELLS OF FIMBRIAE SWEEP SECONDARY OOCYTE INTO INFUNDIBULUM OF UTERINE TUBE

    3) OOCYTE PASSES INTO AMPULLA OF UTERINE TUBE AS RESULT OF PERISTALSIS; MOVES TOWARD UTERUS

    4) FERTILIZED WITHIN 12 HOURS AFTER OVULATION, CANNOT AFTER 24 HOURS
  14. SPERMATOGENESIS (4)
    1) AT PUBERTY, SPERMATOGONIA PROLIFERATE BY MITOTIC DIVISION

    2) SPERMATOGONIA TRANSFORM INTO PRIMARY SPERMATOCYTES

    3) 1*SPERMATOCYTES UNDERGO 1ST MEITIC DIVISION TO FORM TWO 2*SPERMATOCYTES

    4) 2*SPERMATOCYTES UNDERGO 2ND MEIOTIC DIVISION TO FORM 4 HAPLOID SPERMATIDS
  15. PHASES OF FERTILIZATION (6)
    1) SPERM PENETRATES CORONA RADIATA USING ACROSOMAL ENZYMES & TAIL

    2) PENETRATES ZONA PELLUCIDA USING ACROSOMAL ENZYMES. ZONA REACTION FROM OOCYTE STOPS OTHER SPERM

    3) FUSION OF SPERM & OOCYTE PLASM MEMBRANES

    4) COMPLETION OF OOCYTE 2ND MEIOTIC DIVISION. FORMATION OF FEMALE PRONUCLEUS AND 2ND POLAR BODY

    5) FORMATION OF MALE PRONUCLEUS; BOTH MALE & FEMALE REPLICATE DNA

    6) PRONUCLEI FUSE TO FORM ZYGOTE
  16. FROM FORMATION OF ZYGOTE TO MORULA
    1) AFTER THE 9-CELL STAGE, BLASTOMERES CHANGE SHAPE AND ATTACHMENTS TO UNDERGO COMPACTION (REQUIRED TO SEGREGATE INNER CELL MASS GIVING RISE TO EMBRYO PROPER)

    2) MORULA ENTERS THE UTERUS ABOUT 3 DAYS AFTER FERTILIZATION
  17. WHAT IS CLEAVAGE?
    RAPID MITOTIC DIVISIONS OF THE ZYGOTE RESULTING IN EMBRYONIC CELLS CALLED BLASTOMERES
  18. WHAT IS A MORULA?
    EMBRYO CONSISTING OF 12-32 BLASTOMERES
  19. BLASTOCYST FORMATION (3)
    1) FLUID-FILLED BLASTOCYSTIC CAVITY APPEARS INSIDE MORULA ABOUT 4 DAYS AFTER FERTILIZATION

    • 2) BLASTOMERES SEPARATE INTO 2 GROUPS:
    • ---TROPHOBLAST FORMS A THIN OUTER CELL LAYER WHICH GIVES RISE TO EMBRYONIC PLACENTA
    • ---INNER CELL MASS (EMBRYOBLAST) MADE OF CENTRALLY LOCATED BLASTOMERES GIVING RISE TO EMBRYO

    3) CONCEPTUS NOW CALLED BLASTOCYST; AFTER ABOUT 2 DAYS THE ZONA PELLUCIDA DEGENERATES AND THE BLASTOCYST "HATCHES"
  20. EARLY STAGES OF IMPLANTATION (3)
    1) ABOUT 6 DAYS AFTER FERTILIZATION, BLASTOCYST ATTACHES TO ENDOMETRIAL ENDOTHELIUM AT POINT CLOSEST TO INNER CELL MASS (EMBRYONIC POLE)

    • 2) TROPHOBLAST PROLIFERATES AND DIFFERENTIATES INTO 2 LAYERS:
    • --- INNER LAYER CALLED CYTOTROPHOBLAST
    • --- OUTER MULTINUCLEATED LAYER CALLED SYNCYTIOTROPHOBLAST WHICH INVADES ENDOMETRIUM AND RELEASES ENZYMES ALLOWING BLASTOCYST TO BURROW

    3) DAY 7 AFTER FERTILIZATION, PRIMARY ENDODERM (HYPOBLAST) DELAMINATES FROM THE EMBRYOBLAST ON THE DEEP SURFACE FACING THE BLASTOCYSTIC CAVITY
  21. FUNCTIONS OF THE SYNCYTIOTROPHOBLAST (STB) DURING IMPLANTATION (7)
    1) INVADES ENDOMETRIAL CONNECTIVE TISSUE; THESE CELLS MUST BE IN RECEPTIVE STATE FOR INVATION

    2) SPECIALIZED DECIDUAL CELLS OF ENDOMETRIUM DIE AND ARE ENGULFED BY STB FOR FOOD (GLYCOGEN AND LIPIDS)

    3) PRODUCES hCG WHICH MAINTAINS HORMONAL ACTIVITY OF CORPUS LUTEUM

    4) LACUNAE FORM EITHIN STB AND FILL WITH BLOOD WHICH PROVIDES FOOD

    5) ERODED ENDOMETRUAL CAPILLARIES COMMUNICATE WITH THE LACUNAE AND ESTABLISH THE PRIMORDIAL UTEROPLACENTAL CIRCULATION

    6) DECIDUAL CELLS REACTION OF THE ENDOMETRIUM PRIVIDES IMMUNOLOGIAL PROTECTION FOR BLASTOCYST

    7) 12 DAYS AFTER FERTILIZATION: LACUNAR NETWORKS FORM WITHIN STB
  22. ECTOPIC PREGNANCY
    IMPLANTATION OUTSIDE OF UTERUS

    >90% OF THESE OCCUR IN AMPULLA AND ISTHMUS OF URERINE TUBE (TUBAL PREGNANCY)
  23. ABDOMINAL PREGNANCY
    BLASTOCYST EXPELLED INTO THE PERITONEAL CAVITY AND IMPLANTS IN THE RECTOUTERINE POUCH
  24. PLACENTA PREVIA
    BLASTOCYST IMPLANTS NEAR THE THE INTERAL OS "OPENING" OF THE UTERUS

    PLACENTA COVERS OS -- THUS PLACENTA WILL PRECEDE THE BABY IN DELIVERY
  25. AMNIOTIC CAVITY
    * WEEK 2

    *APPEARS AS SPACE IN EMBRYOBLAST (INNER CELL MASS)

    * CELLS MIGRATE FROM THE EPIBLAST AND FORM THE AMNION
  26. EMBRYONIC DISK
    * WEEK 2

    * EPIBLAST FORMS FLOOR OF AMNIOTIC CAVITY CONTINUOUS WITH AMNION

    * HYPOBLAST FORMS ROOF OF EXOCOELOMIC CAVITY

    * PRECHORDAL PLATE (DAY 14) FORMS AS ATHICKENED AREA OF HYPOBLAST. INDICATES FUTURE SITE OF MOUTH.
  27. PRIMARY UMBILICAL VESICLE (PUV)
    * WEEK 2

    * CELLS OF HYPOBLAST AND EXOCOELOMIC MEMBRANE LINE THE PUV (YOLK SAC)

    * EXTRAEMBRYONIC COELOM SURROUNDS AMNION AND UMBILICAL VESICLE, AND BECOMES LINED WITH EXTRAEMBRYONIC MESODERM

    * ENDOMETRIAL CELLS MIGRATE FROM HYPOBLAST TO FORM SECONDARY UMBILICAL VESICLE; PUV PINCHES OFF AND SHRINKS/DISAPPEARS
  28. PRIMARY CHORIONIC VILLI
    * WEEK 2

    * CYTOTROPHOBLAST CELLS PROLIFERATE AND REARRANGE TO FORM "FINGERS" THAT PROJECT INTO THE SYNCYTIOTROPHOBLAST

    * PART OF CHORIONIC SAC DEVELOPMENT
  29. DIVISIONS OF EXTRAEMBRYONIC MESODERM
    * WEEK 2

    * EXTRAEEMBRYONIC SOMATIC MESODERM LINES TROPHOBLAST, COVERS AMNION

    * EXTRAEMBRYONIC SPLANCHNIC MESODERM SURROUNDS UMBILICAL VESICLE

    * PART OF CHORIONIC SAC DEVELOPMENT
  30. CHORION
    * WEEK 2

    * WALL OF CHORIONIC SAC MADE OF EXTRAEMBRYONIC SOMATIC MESODERM + PRIMARY CHORIONIC VILLI + SYNCYTIOTROPHOBLAST

    * EXTRAEMBRYONIC COELOM NOW = CHORIONIC CAVITY

    * PART OF CHORIONIC SAC DEVELOPMENT

    * PART OF CHORIONIC SAC DEVELOPMENT
  31. GASTRULATION
    WEEK 3

    FORMATION OF GERM LAYERS

    • CONVERTS BILAMINAR EMBRYONIC DISC INTO TRILAMINAR EMBRYONIC DISK:
    • ---ECTODERM
    • ---MESODERM
    • ---ENDODERM

    BEGINNING OF MORPHOGENESIS

    BEGINS WITH PRIMITIVE STREAK ON DORSAL SURFACE OF EPIBLAST

    EMBRYO IS NOW CALLED A GASTRULA
  32. EMBRYONIC ECTODERM
    WEEK 3

    MOST SUPERIOR PART OF TRILAMINAR EMBRYONIC DISK. BETWEEN AMNION (DORSAL SIDE) AND MESODERM (VENTRAL SIDE)

    GIVES RISE TO EPIDERMIS, CENTRAL AND PERIPHERAL NERVOUS SYSTEMS, AND RETINA
  33. EMBRYONIC MESODERM
    WEEK 3

    MEDIAL PART OF TRILAMINAR EMBRYONIC DISK BETWEEN ECTODERM AND ENDODERM

    GIVES RISE TO SMOOTH MUSCLE COATS, CONNECTIVE TISSUE AND VESSELS, MOST OF CARDIOVASCULAR SYSTEM, BLOOD CELLS AND BONE MARROW, SKELETON, STRIATED MUSCLES, REPRODUCTIVE AND EXCRETORY ORGANS
  34. EMBRYONIC ENDODERM
    WEEK 3

    MOST INFERIOR PART OF TRILAMINAR EMBRYONIC DISK. BETWEEN EMBRYONIC MESODERM AND HYPOBLAST.

    GIVES RISE TO EPITHELIAL LININGS OF RESPIRATORY PASSAGES AND GASTROINTESTINAL TRACT, AND TO GLANDULAR CELLS OF ASSOCIATED ORGANS
  35. PRIMITIVE STREAK
    WEEK 3

    APPEARS CAUDALLY AND MEDIALLY ON DORSAL SIDE OF EPIBLAST

    PRIMITIVE GROOVE AND PIT ALLOW ID OF CRANIAL/CAUDAL AND LEFT/RIGHT AXES

    MESENCHYMAL CELLS FORM EITHER MESODERM OR ENDODERM (MUST DISPLACE HYPOBLAST)

    REGRESSES AND DISAPPEARS EARLY ON WEEK 4
  36. SACROCOCCYGEAL TERATOMA
    MOST COMMON TUMOR IN NEWBORNS

    RESULTS FROM PERSISTENCE OF PRIMITIVE STREAK
  37. NOTOCHORDAL PROCESS
    WEEK 3

    FORMED FROM INVAGINATING MESENCHYMAL CELLS OF EPIBLAST THAT MIGRATE CRANIALLY ALONG MIDLINE

    DORSAL CELLS PERSIST AS FLAT NOTOCHORDAL PLATE, WHICH FOLDS TO BECOME THE RIGID NOTOCHORD
  38. NOTOCHORDAL CANAL
    WEEK 3

    LUMEN OF NOTOCHORDAL PROCESS
  39. PRECHORDAL PLATE
    WEEK 3

    SMALL CIRCULAR STRUCTURE CRANIAL TO NOTOCHORDAL PROCESS WHERE ECTO AND ENDODERM ARE IN CONTACT

    BLOCKS EXTENSION OF NOTOCHORDAL PROCESS CRANIALLY

    PRIMORDIUM OF THE OROPHARYNGEAL MEMBRANE (ORAL CAVITY)
  40. NEURENTERIC CANAL
    WEEK 3

    TEMPORARY COMMUNICATION BETWEEN AMNIOTIC AND UMBILICAL VESICLE CAVITES

    LAST AND TEMPORARY STRUCTURE OF NOTOCHORDAL CANAL
  41. NOTOCHORD
    WEEK 3

    FORMED IN SEVERAL STEPS DURING GASTRULATION BY MESENCHYMAL MESODERM CELLS

    INDUCES OVERLYING ECTODERM TO BECOME NEURAL PLATE

    INDICATES FUTURE SITE OF VERTEBRAL BODIES
  42. NEURAL PLATE
    WEEK 3

    FORMED FROM ECTODERM INDUCED BY THE NOTOCHORD

    PRIMORDIUM OF THE CNS
  43. CLOACAL MEMBRANE
    WEEK 3

    CAUDAL TO PRIMITIVE STREAK

    MADE UP OF FUSED ENDO AND ECTODERM

    PRIMORDIUM OF ANUS
  44. SOMITE FORMATION
    WEEK 3

    EMBRYONIC MESODERM ON EACH SIDE OF NOTOCHORD PROLIFERATES TO FORM COLUMN OF PARAXIAL MESODERM

    END OF 3RD WEEK, PARAXIAL MESODERM DIVIDES INTO BLOCKS CALLED SOMITES

    SOMITES GIVE RISE TO MOST OF THE AXIAL SKELETON AND ASSOCIATED MUSCLES, AND TO THE ADJACENT DERMIS OF SKIN
  45. CLINICAL RELEVANCE OF SPONTANEOUS ABORTIONS
    OCCURS NATRALLY

    MOST COMMON DURING 3RD WEEK

    15% OF PREGNANCIES END BY THIS

    50% RESULT FROM CHROMOSOMAL ABNORMALITIES OF THE CONCEPTUS

    CAN BE CAUSED BY A TRISOMY AS A RESULT OF NONDISJUNCTION (EXCEPTION, DOWN SYNDROME)

    SPORADIC AND RECURRENT SPONTANEOUS ABORTIONS ARE COMMON GYNECOLOGICAL PROBLEMS
  46. SIRENOMELIA
    CAUDAL DYSGENESIS

    INSUFFICIENT MESODERM IN THE CAUDAL REGION OF EMBRYO DUE TO DISRUPTION OF GASTRULATION

    • RESULTS IN:
    • ---ABNORMAL LUMBOSACRAL VERTEBRAE
    • ---HYPOPLASIA AND FUSION OF LOWER LIMBS
    • ---RENAL AGENESIS
    • ---IMPERFORATE ANUS
  47. SITUS INVERSUS
    TRANSPOSITION OF THE VISCERA IN THE THORAX AND ABDOMEN

    MAY BE DUE TO GENETIC ABNORMALITIES IN CILIA (KARTAGENER SYNDROME) WHICH ARE PRESENT ON THE CELLS OF THE PRIMITIVE NODE
  48. SACROCOCCYGEAL TERATOMA
    DEVELOPS FROM PLURIPOTENT CELLS THAT ARE REMNANTS OF THE PRIMITIVE STREAK

    MAY CONTAIN TISSUES DERIVED FROM ALL THREE GERM LAYERS

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