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Microanatomy > Embryology & Gametogenesis > Flashcards

Embryology & Gametogenesis Flashcards

1
Q

Cleavage

A

Initial cell division and blastomeres
Unicellular zygote divides by mitosis to become multicellular Embryo
Each daughter cell is called a blastomere
No increase in size so termed as cleavage

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2
Q

The morula

A

Blastomeres continue to divide into a compact ball of 16-31 cells within the zone pellucid
Looks like a mulberry

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3
Q

The blastocyst

A

As the morula grows a cavity (blastocoele) forms within it

Inner cell mass (embryo blast) surrounded by outer cells (trophoblast)

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4
Q

Blastocyst: inner cells

A

Embryoblast forms entire embryo
Forms bilaminar disc of Epiblast (dorsal) and Hypoblast (ventral)
Establishes dorsoventral axis

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5
Q

Blastocyst: Outer cells

A

Trophoblast will expand to form the extra embryonic membranes (placentation)

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6
Q

Stem cells

A

Specialized cells capable of self renewal; they may be-

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7
Q

Totipotent

A

From zygote- can form every cell in embryo and trophoblastic placenta

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8
Q

Pluripotent

A

from inner cell mass- can form all embryonic cells (not trophoblastic placenta)

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9
Q

Multipotent

A

Can form a limited number of subtypes within a broader category (epithelial cells, WBCs etc)

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10
Q

Unipotential

A

can form a specific cell type

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11
Q

Migration, differentiation

A

a complex interaction controlled by gene interactions and cell signaling

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12
Q

The zygote contains

A

1 cell

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13
Q

Gastrulation

A

Inner cell mass –> Bilaminar disc –> trilaminar disc

Cells from epiblast migrate leaving a primitive streak (craniocaudal axis)

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14
Q

Trilamminar disk

A

Renamed as 3 germ layers:
Ectoderm
Mesoderm
Endoderm

These layers are formed by migration of epiblast cells

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15
Q

Ectoderm derivatives

A

Epidermal structures (skin), lining of oral, nasal cavity and anus. Nervous system (neuroectoderm - specialized ectoderm)

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16
Q

Mesoderm derivatives

A

Connective tissues, muscle tissue, mesothelium, cardiovascular system, urogenital tract

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17
Q

Endoderm derivatives

A

Epithelial lining and glands of digestive and respiratory system

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18
Q

Neural tube

A

Mesoderm forms notochord under primitive streak
Notochord induces ectoderm to form neural tissue (neuroectoderm)
Neural tube and neural cost cells formed; early somites formed
Cranial part of the neural tube–> brain
Caudal part of neural tube –> spinal cord

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19
Q

Embryonic folding

A

Cranial-caudal and lateral body folds create the head, tail, primitive anus and mouth

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20
Q

The yolk sac is lined by

A

endoderm

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21
Q

Mesoderm differentiates further

A

Axial: notochord
Paraxial: somites
Intermediate: urogenital system
Lateral plate: somatic and splanchnic mesoderm

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22
Q

Somites

A

Dermatome –> dermis
Myotome –> muscles
Sclerotome –> vertebrae and ribs

Somatic and splanchnic mesoderm separate with formation of coelom (peritoneum) in between
Limb buds- all other cartilage and bones of the body and limbs are formed from lateral plate mesoderm
Skull is formed of a combination of lateral plate mesoderm, paraxial (somite) mesoderm and neural crest cells

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23
Q

The smooth muscle of the GIT arise from

A

Splanchnic mesoderm

24
Q

Pluripotent stem cells arise from the

A

inner cell mass

25
Q

Summary of embryology

A

Sperm +ovum =pronucleum –> zygote –> morula –> blastocyst —> trophoblast and inner cell mass
Trophoblast –> placenta
Inner cell mass –> epiblast –> ectoderm, mesoder, endoderm –> foetus or talk sac
Hypoblast –> yolk sac

26
Q

Teratogens

A

Any age or factor that can cause congenital (present at birth) anomalies in an embryo or fetus
Genetic factors
Radiation
Chemical agents (nicotine, drugs, alcohol)
Infectious agents (bovine viral diarrhea virus)
Hormones (anti-paramesonephric duct hormone in freemartins)

27
Q

Teratogenic influences on development

A

At predifferentiation stageL embryo dies
During organogenesis stage: structural defects (major morphologic defects)
During fetal growth stage: affects functional maturation (and minor structural defects)

28
Q

At which of the following stages does action by a teratogen result in the most severe consequences

A

Predifferentiation

29
Q

Which are part of the brain

A

Cerebrum
Cerebellum
Brainstem
Pineal gland

30
Q

Gametogenesis

A

Production of haploid (1N) germ cells at the right place at the right times
Gametes have 1/2 the chromosome number
Spermatozoa or ova

31
Q

Fertilization

A

Fusion of 2 haploid gametes creates a diploid (2N) zygote with full complement of chromosomes

32
Q

Embryological origins of germ cells

A

Primordial germ cells from yolk sac and allantois migrate to genital ridge via dorsal mesentery –> become biopotential gonad

33
Q

Male XY

A

Seminiferous cords (no lumen)
-spermatogonia
-supporting sertoli cells
Interstitial cells of leydig

34
Q

Female XX

A

Primordial germ cells (oogonia) form peripherally arranged primordial follicles in a stroma
Primordial follicles all formed in the developing embryo before birth

35
Q

Formation of duct systems

A

Male: mesonephric duct
-forms epididymis, ductus deferens

Female: paramesonephric duct
-formed uterine tubes, uterus, cervix

Anti-mullerian hormone produced by sertoli cells directs male development

36
Q

The gonads arise from

A

intermediate mesoderm

37
Q

The cell cycle

A

G1 phase
S phase
G2 phase
M phase

38
Q

Mitosis

A

DNA duplicates in S phase of interphase
Each chromosome has 2 sister chromatids
Final products are 2 2n
Clones of the original cell

39
Q

Meiosis in males

A

2 cells ends in 4 haploid cells at end of meiosis 2

40
Q

Spermatogenesis

A
  1. Spermatocytogenesis: Spermatogonia divide by mitosis several times and produce primary spermatocytes
  2. Meiosis: primary spermatocytes divide by meiosis into secondary spermatocytes and spermatides
  3. Spermiogenesis: transformation (metamorphosis) of spermatids into spermatozoa
41
Q

Meiosis in females

A

Stops in prophase 1 until puberty- primary oocyte
puberty meiosis continues
Stops on metaphase 2 in oviduct until sperm contact then it will complete meiosis 2

42
Q

Oogenesis

A

Production of an ovum

  1. oogonia- prenatal mitosis produces primary oocytes
  2. Primary oocytes (diploid) arrested in meiosis I until puberty
  3. After puberty- orderly maturation of the oocyte and supporting cells within a protective ovarian follicle under hormonal influence
  4. Ovarian follicle- meiosis I is completed just before ovulation to produce secondary oocyte and 1st polar body except for dogs and mares (these ovulate primary oocytes)
  5. Meiosis II starts immediately but arrests until
  6. In oviduct, secondary oocyte (haploid) awaits fertilization
  7. Meiosis II completed on sperm contact (2nd polar body is produced)
  8. Result is ovum (haploid) and 2nd polar body (haploid)

Polar bodies are remnant of cytoplasm and nucleus formed during meiosis

43
Q

Mitosis vs meiosis

A

Mitosis results in formation of 2 diploid daughter cells
Meiosis results in formation of 4 haploid cells and exchange of genetic material

Gametes are haploid and of different genetic constitution

44
Q

Common features of male and female gametogenesis

A

Occur in specialized sexually dimorphic organs (testis/organs)
Multiplication of spermatogonia and oogonia by mitosis
Formation of gametes by meiosis- importance of crossing over and independent assortment for variability= extensive morphological variation (evolution)
Incapacity of surviving for very long if fertilization does not occur

45
Q

Differences of male and female gametogenesis

A

Sperm: supply continuously renewed

  • one primary spermatocyte produces 4 sperm
  • Gametogenesis results in small cells
  • Motile cells
  • X or Y sex chromosome

Oocyte: all present at birth

  • one primary oocyte produces 1 ovum
  • Gametogenesis results in a large cell
  • immotile cell
  • x chromosomes only
46
Q

Chromosome number halved during

A

meiosis 1

47
Q

Ovulation

A

Oocyte departs the ovary leaving behind a structure known as the corpus hemorrhagicum- a (transient structure) that becomes the corpus luteum of luteal cells

48
Q

Spermatozoa

A 
Haploid cell (nucleus) for fertilization
Motility to deliver the nucleus to the ovum
Energy
Mechanism of entry into ovum
49
Q

Maturation of sperm

A

acrosome covered by extension of pm

50
Q

Spermatogenesis: Histology

A

Peripheral on basement membrane (basolateral): spermatogonia -divid and produce more spermatogonia and primary spermatocyte
-sertoli cells- support

Towards Lumen (apical): primary spermatocytes (secondary spermatocytes are short lived)
-round and elongated spermatides

Lumen: sperm

51
Q

Spermatogenesis: metamorphosis

A

Transformation of the round spermatid to a spermatozoon

  • formation of the acrosome from golgi vesicles (contains enzymes)
  • condensation of the nuclear chromatin
  • outgrowth of a motile tail (flagellum-from centrioles) surrounded by mitochondria
  • loss of excess spermatid material (cytoplasm, water, organelles)
52
Q

Spermatozoon morphology

A

Head: nucleus, plasma membrane, acrosome (enzymes)
Mid piece: spirally arranged mitochondria. Intense energy production
Tail: Motility. classified’s flagellum/cilia structure. Axoneme- outer ring of 9 doublet microtubules

53
Q

Fertilization: capacitation

A

Occurs in uterine environment
Biochemical change in response to uterine secretions
Hyperactivity of the spermatozoon tail
Allows acrosomal reaction to occur

54
Q

Fertilization: Acrosome reaction

A

enzymes released ti digest zone pellucida

55
Q

Fertilization: cortical reaction

A

Sperm contact with oocyte plasma membrane
Release of proteases from cortical granules in oocyte
Zona pellucida is then a barrier to other seem penetration

56
Q

Fertilization

A

Nuclear material of spermatozoon and ovum are called pronuclei
Syngamy

57
Q

Syngamy

A

Union of male and female haploid pronuclei. They merge restoring diploid set of chromosomes and enter the first mitotic division= zygote

Microanatomy (21 decks)

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