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Block One > Body Plan > Flashcards

Body Plan Flashcards

1
Q

6 adaptations that allow mammalian embryo to survive inside another organism

A

Placenta, umbilical vein, ductus venous, foramen ovale, ductus arteriosus, umbilical arteries

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2
Q

Internal iliac arteries

A

Umbilical arteries branch to form these and parts remain to supply the bladder

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3
Q

Steps to embryonic development

A
  1. Common organization (all embryos in this stage look alike)
  2. The three germ layers (ectoderm, mesoderm, endoderm)
  3. Embryonic folding (forms tubular organs and cavities)
  4. Building blocks (epithelial, mesencymal, and blood cells)
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4
Q

3 principal axes of body plan

A

Cranial-Caudal, Dorsal-Ventral, Left-Right

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5
Q

Embryonic development stages

A

Zygote -> blastocyst -> baliminar disc ->trilaminar disc

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6
Q

Mesoderm differentiation

A

Notochord, paraxial intermediate, and lateral mesoderm (lateral mesoderm will split into somatic and splanchnic mesoderm

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7
Q

Cranial-caudal folding

A

Brings most cranial heart into thoracic (more caudal) position. Brings septum transversum caudal to heart (septum transversum is first division of embryonic coelom)

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8
Q

Lateral folding

A

Closes the embryo and forms tubular organs like gut tube and heart. Incorporates extra embryonic coelom into the embryo thereby forming first intraembryonic body cavity (ie a coelomic cavity)

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9
Q

Morphogenetic

A

Process of shaping body and its parts

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10
Q

Gastrulation

A

Process of embryonic folding, transforms embryo into 3-d cylindrical shape and forms body cavities

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11
Q

Embryogenesis

A

Choreographed interplay of cells and processes necessary in the development of the embryo

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12
Q

Requirements to successfully complete embryonic development

A

1 survival
2 change (ie development)
3 prepare for birth

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13
Q

Blood vessels fetus utilizes for nutrient and oxygen uptake

A

Umbilical vein and umbilical artery

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14
Q

Placenta organ replacement

A

Placenta is lungs, kidneys and liver of developing fetus; contains tissues and vessels from both the embryo (chorionic plate) and mother (basal plate). Placenta mostly made of cells derived from trophoplast

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15
Q

Respritory and digestive system adaptations for speeding up oxygen delivery to fetus

A

Foramen ovale and ductus arteriosus (respritory) and ductus venosus (digestive) provide short cuts for placental blood to get to fetus quickly by bypassing liver and lungs

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16
Q

Ductus venosus

A

Placental blood is returned to fetus by 2 large umbilical veins that join as one when entering body at the navel, the single abdominal umbilical vein runs forward to penetrate liver and bypasses Hypatic circulation via the ductus venosus which tunnels through the liver joining caudal venacava

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17
Q

Blood flow in placenta

A

Placental blood returns to fetus in 2 umbilical veins which become one in navel -> ductus venosus -> caudal vena cava (now mixes super oxygenated placental blood with deoxygenated blood returning from hind part of body) ->foramen ovale -> 2 branches
Branch one: foramen ovale -> right atrium -> right ventricle -> pulmonary trunk -> ductus arteriosus -> descending aorta -> umbilical artery -> placenta -> umbilical vein

Branch two: foramen ovale ->left atrium -> left ventricle -> aorta -> brain/ upper half of body -> umbilical artery -> placenta -> umbilical vein

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18
Q

Umbilical arteries

A

Carry deoxygenated blood from descending aorta back to placenta for oxygenation. Umbilical arteries branch fo form internal iliac arteries

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19
Q

Changes in circulation following birth

A
  1. Removal of placenta -> drop in body temperature constricting and closing umbilical vein, change in resistance to blood flow (higher resistance) leads to no blood flowing in umbilical vein or ductus venosus which eventually closes
    2.first breath expands lung decreasing resistance to blood flow in lung dropping blood pressure in right atrium and right ventricle leading to close of foramen ovale
    Rise in oxygen level of the blood leads to smooth muscle contraction which closes ductus arteriosus.
    Loss of prostaglandin from removal of placenta leads to closing of umbilical arteries (distal part will become round ligament of bladder0, proximal part remains and supplies some blood to cranial part of bladder
    Stump of umbilical vein outside abdomen shrivels and intraabdominal part will transform to round ligament of the liver
    Ductus arteriosus- converted into fiborous structure known as ligamentum arteriosum
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20
Q

Patent ductus arteriosus

A

If ductus arteriosus abnormally persists after birth and fails to close poorly oxygenated blood from right ventricle will enter systemic circulatory system without being oxygenated in the lungs. This is most common congenital cardiovascular birth defect in dogs.

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21
Q

Location of structure in adult and embryonic body should be described in relation to the

A

CNS

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22
Q

Establishment of axes

A

Originates just after fertilization
First axis to be established- Cranioventral-caudal
2nd to be established- dorso-ventral
3rd axis to be established - left-right

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23
Q

Left right axis is critical to

A

Formation of heart and gastrointestinal tract
Heart on left
Stomach on left
Spleen on left
Liver on right
Vasculature inflow of heart on right, outflow on left

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24
Q

Amnion

A

Water sac, allows embryo to float in fluid environment that protects it from shock an desiccation

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25
Q

Yolk sac

A

Membrane derived from the embryo, enables nutrient uptake, development of circulatory system

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26
Q

Allantois

A

Stores waste product, developers at caudal end of embryo

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27
Q

Chorion

A

Forms the placenta, contains blood vessels that exchange gases with outside enviornment

28
Q

Blastocyst

A

Fluid filled sphere steps:
Zygote becomes morula (ball of cells) (consists of small group of inner cells surrounded by large group of outer cells)
Outer cell layer forms trophoblast which secretes fluid into morula making fluid filled cavity
Inner cells become positioned on one side of the ring of trophoblast cells to form aggregate of inner cell mass
These steps form blastocyst

29
Q

Inner cell mass vs trophoblast

A

Cells in inner cell mass will become embryo cells in trophoblast will become placenta

30
Q

Hypoblast

A

Separation of some of the cells in inner cell mass form this layer. The cells of hypoblast line the fluid-filled cavity where they give rise to extra embryonic endoderm which forms yolk sac

31
Q

Epiblast

A

Remaining inner cell mass tissue above hypoblast; the embryo will come entirely from the epiblast

32
Q

Amniotic cavity

A

Epiblast cell layer will split into embryonic epiblast and other epiblast cells which will line amniotic cavity. Once amnion is fully lined it fills with amniotic fluid

33
Q

Epiblast and hypoblast

A

Together they are referred to as the bilaminar disc (ie bilaminar embryonic disc). The two layers are sandwiched between other two layers of the disc the yolk sac and the amniotic cavity

34
Q

Trilaminar disc

A

Cells of epiblast give rise to three germ layers endoderm, mesoderm, and ectoderm. Formation begins with the primitive streak (depression in epiblast) which will define major body axes of the embryo as it extends in cranial caudal direction and divides the embryo into a left and right half. Epiblast cells migrate dorsal to ventral

35
Q

Endoderm formation

A

After the formation of the primitive streak first epiblast cells migrate and displace hypoblast cells of yolk sac

36
Q

Mesoderm formation

A

Epiblast cells that follow cells becoming endoderm become mesoderm

37
Q

Ectoderm formation

A

Remaining epiblast cells after primitive streak formation and endoderm and mesoderm cells migrate in formation of 3 germ layers

38
Q

Notochord formation

A

Central region of the trunk mesoderm forms the notochord.
Major functions of notochord: establishing crainial caudal body axis and inducing and patterning future neural tube (which becomes adult CNS)

39
Q

Paraxial mesoderm formation

A

This flanks the notochord on both sides cells in this region form somites which are mesodermal blocks that will form the vertebrea

40
Q

Intermediate mesoderm

A

Further from midline than paraxial mesoderm, this will form urogenital system including kidneys, gonads, and associated ducts

41
Q

Lateral mesoderm

A

Furthest from the notochord. This will further separate into splanchnic mesoderm and somatic mesoderm

42
Q

Splanchinic mesoderm

A

Deepest lateral mesoderm layer, adjacent to endoderm. Forms smooth muscles and connective tissues of digestive and respiratory organs and also forms the heart

43
Q

Somatic mesoderm

A

Superfical layer of lateral mesoderm, adjacent to ectoderm and closer to body wall. Participates in development of body wall tissues

44
Q

Spanchopleure

A

Double layer formed by association of splanchinic mesoderm with endoderm

45
Q

Somatopleure

A

Double layer formed by association of somatic mesoderm with the ectoderm (body wall)

46
Q

Splanchopleure and somatopleure

A

Splanchnopleure (surrounds gut and heart) somatopleure forms body wall; together these form first body cavity (space in between them)

47
Q

Embryonic folding

A

Fold trilaminar flat embryo into mos or less of a cylindrical tube, closes initially flat embryo and closes initially flat organ primordial giving rise to tubular organs. Folding also forms body cavities which are more tubes

48
Q

Extraembryonic membranes in embryonic folding

A

Body cavities are formed during folding which is acomplished by segregating embryo from extraembryonic membranes, two water balloons are either obliterated (yolk sac and placenta) or incorporated (like coelom which is origin of body cavities) into embryo

49
Q

How does Embryonic folding happen

A

Embryonic folding is primarily achieved by differential rates of growth in different regions of the embryo. Because trilaminar embryo is flat have to make a closed tube by closing all directions so Cranio-caudal folding and lateral (ie left right) fold occur at approximately the same time

50
Q

Cranial-caudal folding

A

Happens at cranial and caudal edges of embryo.
Cranial edge- we have repositioning (dropping from most cranial to more caudal position) of future opening of mouth, heart, primative thoracic cavity, and a wedge of mesoderm (septum transversum which forms diaphragm)
Assures the following
1. Forms ventral surface of future face, neck, and chest
2. Assures heart within the thoracic cavity is below beck (brings heart from most cranial into thoracic position)
3. Repositioning of septum transversum divides for first time the coelom into two cavities, thoracic (includes pericardial and pleural) and peritoneal (abdominal) cavity
Processes at caudal edge bring future urinary tract and gut openings into ventral position

51
Q

Lateral folding

A

AKA left right folding
Accomplishes the following
1. Closes body wall (somatopleure) of embryo ventrally
2. Closes initially flat organ primordial (splanchnopleure) ventrally to form tubular organs
3. Forms first body cavity (coelom), flaps of mesoderm (splanchnopleure and somatopleure) fold toward ventral midline along with coelom and meet and merge. The coelom between them which had been extraembryonic is now incorporated in the embryo and is intraembryonic this single large cavity will later be subdivided into separate thoracic and peritoneal cavities

52
Q

Lateral folding at level of the navel

A

This closes the embryo at that level fuses midgut tube (forms the intestine) and forms the coelom that later becomes the abdominal cavity

53
Q

Lateral folding at level of future heart

A

Closes embryo at that level, fuses heart tube, forms coelom that will become the pericardial cavity
This can also be referred to as lateral folding at level of the foregut

54
Q

Dorsal mesentery

A

“Neck” of splanchnic mesoderm which remains after folding of splanchnopleure and somatopleure this will suspend the gut tube from the dorsal body (abdominal) wall; the newly formed gut tube is suspended within the coelom from dorsal abdominal body wall by dorsal mesentery, this divides the coelom into left and right side

55
Q

Dorsal mesocardium

A

Connects heart tube to dorsal portion of the body (thoracic) wall

56
Q

Coelomic cavity divisions

A

Peritoneal cavity, pericardial cavity, pleural cavities. Initial coelom looks like a U, caudal region of U shaped coelom forms left and right peritoneal cavity. Cranial region of U-shaped coelom will become pericardial cavity.

57
Q

Septum transversum

A

Formation of this separates left and right peritoneal (abdominal) cavities from pericardial cavity, cranial caudal folding will eventually bring this initially cranial septum to a position caudal to the heart where it will form diaphragm
First cranial to caudal division of coelom

58
Q

Thoracic cavity separation

A

Separates into pericardial and pleural cavities by growth of pleuropericardial folds. These communicate after separation via left and right pericardial-peritoneal canals

59
Q

Congenital diaphragmatic hernias

A

Closing of pericardial-peritoneal canals is acomplished by growth of pleuroperitoneal folds which fuse with septum transversum and seal left and right canals, left canal is larger than right canal and takes longer to close which is why more of these occur on the left side

60
Q

Three major cell types that make up embryo

A

Epithelial cells (majority of cells), mesenchymal cells, and endothelial cells

61
Q

Epithelial cells

A

These are super organized and the majority of cells. Usually form sheets or rows of cells with repeating shapes, these are very INVOLVED IN FOLDING Always found in big groups and fold together as a long sheet, tightly connected (cell cell adhesion), good for creating a barrier. These are polarized (asymmetrical) with apical structures like microvilli specialized for absorbtion and secretion, many have cillia, basal structures secrete matrix molecules that form a condensed tightly bound basement membrane

62
Q

Mesenchymal cells

A

Have random shape, love to hang out alone, migrate alone or in small groups, transiently touch each other, these are in connective tissue of embryo, indistinguishable from fibroblasts (which are found in adult mature tissues); these cells are surrounded on all sides by mesh work of extracellular matrix which contains high proportion of collagens . Can be stationary or highly motile. Can be invasive because have ability to penatrate ECM

63
Q

Can cells change type during develpment?

A

Yes epithelial cells can become mesenchymal cells and visa versa during development

64
Q

Epithelial cell and mesenchymal cell interactions

A

Are essential for develpment of both types of cells. If an epithelium doesn’t receive appropriate signals from adorning mesenchymal populations it will not continue to develpment and will usually denigrate, the opposite is true as well

65
Q

Stages of embryonic development

A

Zygot -> blastocyst -> bilaminar disc -> trilaminar disc

66
Q

Mediastinum formation

A

Formed internally by dorsal and ventral mesenteries of the esophagus

Block One (31 decks)

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