Basic - Primitive Heart Tube: Difference between revisions

Latest revision as of 10:19, 12 November 2015

Begin Basic

Primitive Heart Tube

Embryonic Heart Divisions

Vascular Heart Connections

Cardiac Embryology

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The developing blood vessels and heart tube can be seen in an embryo at approximately 18 days

The heart is the first organ to function within an embryo. It starts to function at the beginning of the fourth week when the nutritional and oxygen requirements of the growing embryo can no longer be met by diffusion from the placenta. The heart initially forms from two tubes located bilaterally (on either side) of the trilaminar embryo in the cranial (head) region. The image on the right shows these primitive tubes developing in an embryo approximately 18 days after conception.

When looking down at this early embryo you can see multiple blood islands dispersed throughout the embryo. These will form the early blood vessels. At the most cranial end of the embryonic disc these blood islands are actually the primitive heart tube. From the side you can see one of the heart tubes and heart cavity developing in this position.

Embryonic Folding

The disc-like embryo then undergoes a process of folding, in which both the cranial and lateral parts of the embryo fold ventrally (forwards). This brings the heart-forming region to a ventral (frontal) position. The following animation shows the development of the heart tubes and how embryonic folding brings them to fuse in the midline. (Click image to play on current page or Play video on new page)

<html5media height="720" width="560">File:Heart_folding_002.mp4</html5media>

Back to the basic homepage		Next: Divisions of the Embryonic Heart
		Go to this section in the intermediate level

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Blood Islands: The initial small patches which form within mesoderm that differentiate into both the blood vessel wall and blood cells. These islands enlarge and connect together to form the initial vascular beds.

Caudal: Anatomical term referring to structures that are more towards the tail.

Cranial: Anatomical term referring to structures that are more towards the head.

Dorsal: Anatomical term referring to structures that are more towards the back.

Embryonic disc: A flat two- or three-layered area; the first traces of the human embryo.

Heart cavity: (Also pericardial cavity). The space in which the heart lies. In the adult heart this space diminishes so that the heart wall (visceral pericardium) and cavity wall (parietal pericardium) are continuous.

Lateral: Anatomical term referring to structures that are away from the midline.

Placenta: The developmental organ formed from maternal and fetal contributions in animals with placental development. In human, the placenta at term is a discoid shape "flat cake" shape; 20 cm diameter, 3 cm thick and weighs 500-600 gm. The placenta has many different functions including metabolism, transport and endocrine.

Primitive heart tube: Initial, straight, tube-like structure of the embryonic heart.

Trilaminar embryo: Term used to describe the early three (3) layered embryo following gastrulation when it now has a structure consisting of the 3 germ cell layers: ectoderm, mesoderm, endoderm. In humans, this developmental stage occurs during week 3. Do not confuse the term "germ cell layers" with "germ cells", which refer to the egg and sperm.

Ventral: Anatomical term referring to structures that are more towards the front.

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 [[Image:Basicicon.jpg|left|70px|link=Basic_Cardiac_Embryology]]
 {{Basic Cardiac menu}}
-{{Template:Cardiac_modules}}
+{{Cardiac_modules}}
+[[Image:Basic Heart Development Timeline.jpg|center|800px]]
-[[Image:HeartILP_draft_primitive heart tube.jpg|thumb|right|upright=2|The developing blood vessels and heart tube can be seen in an embryo at approximately 18 days]]The heart is the first organ to function within an embryo. It starts to function at the beginning of the fourth week when the nutritional and oxygen requirements of the growing embryo can no longer be met by diffusion from the placenta.  The heart initially forms from two tubes located bilaterally (on either side) of the trilaminar embryo in the cranial (head) region.  The image on the right shows these primitive tubes developing in an embryo approximately 18 days after conception.
+[[Image:Early Development of Heart Tube.jpg|thumb|right|upright=2|The developing blood vessels and heart tube can be seen in an embryo at approximately 18 days]]The heart is the first organ to function within an embryo. It starts to function at the beginning of the fourth week when the nutritional and oxygen requirements of the growing embryo can no longer be met by diffusion from the '''placenta'''.  The heart initially forms from two tubes located bilaterally (on either side) of the '''trilaminar embryo''' in the '''cranial''' (head) region.  The image on the right shows these primitive tubes developing in an embryo approximately 18 days after conception.
-When looking down at this early embryo, you can see multiple blood islands dispersed throughout the embryo.  These will form the early blood vessels.  At the most cranial end of the embryonic disc, these blood islands are actually the primitive heart tube.  From the side you can see one of the heart tubes and heart cavity developing in this position.
+When looking down at this early embryo you can see multiple '''blood islands''' dispersed throughout the embryo.  These will form the early blood vessels.  At the most cranial end of the '''embryonic disc''' these blood islands are actually the '''primitive heart tube'''.  From the side you can see one of the heart tubes and '''heart cavity''' developing in this position.
 ===Embryonic Folding===
-The disc-like embryo then undergoes a process of folding, in which both the cranial and lateral parts of the embryo fold ventrally (forwards).  This brings the heart-forming region to a ventral (frontal) position.  The following animation shows the development of the heart tubes and how embryonic folding brings them to fuse in the midline.
+The disc-like embryo then undergoes a process of folding, in which both the ''cranial'' and ''lateral'' parts of the embryo fold ventrally (forwards).  This brings the heart-forming region to a '''ventral''' (frontal) position.  The following animation shows the development of the heart tubes and how embryonic folding brings them to fuse in the midline. (Click image to play on current page or [[Media:Heart_folding_002.mp4|Play video on new page]])
+<html5media height="720" width="560">File:Heart_folding_002.mp4</html5media>
+----
+{| width="100%"
+|-
+|width="30%" bgcolor="limegreen"|<big>'''[[Cardiac_Embryology|Back to the basic homepage]]'''</big>
+|
+|width="30%" bgcolor="limegreen" align="right"|<big>'''[[Basic_-_Embryonic_Heart_Divisions|Next: Divisions of the Embryonic Heart]]'''</big>
+|-
+|
+|
+|bgcolor="gold" align="right"|<big>'''[[Intermediate_-_Primordial_Heart_Tube|Go to this section in the intermediate level]]'''</big>
+|}
+{{Template:Glossary}}
+'''Blood Islands:''' The initial small patches which form within mesoderm that differentiate into both the blood vessel wall and blood cells. These islands enlarge and connect together to form the initial vascular beds.
+'''Caudal:''' Anatomical term referring to structures that are more towards the tail.
+'''Cranial:''' Anatomical term referring to structures that are more towards the head.
+'''Dorsal:''' Anatomical term referring to structures that are more towards the back.
+'''Embryonic disc:''' A flat two- or three-layered area; the first traces of the human embryo.
+'''Heart cavity:''' (Also pericardial cavity). The space in which the heart lies. In the adult heart this space diminishes so that the heart wall (visceral pericardium) and cavity wall (parietal pericardium) are continuous.
-<Flowplayer height="540" width="720" autoplay="true">Heart folding 002.flv</Flowplayer>
+'''Lateral:''' Anatomical term referring to structures that are away from the midline.
-From here we can see the primitive heart from a ventral view as it consists of the two tubes.  These tubes fuse together (as seen in the diagram on the right) to form a single, primordial heart tube, situated in the midline of the embryo, ventral to the pharynx.
+'''Placenta:''' The developmental organ formed from maternal and fetal contributions in animals with placental development. In human, the placenta at term is a discoid shape "flat cake" shape; 20 cm diameter, 3 cm thick and weighs 500-600 gm. The placenta has many different functions including metabolism, transport and endocrine.
-===Segments of the Heart Tube===
+'''Primitive heart tube:''' Initial, straight, tube-like structure of the embryonic heart.
-At this stage, the tube already has minor constrictions within it indicating sections of the heart tube that will form parts of the adult heart.  The most caudal (tail end) segment of the heart tube is the sinus venosus which will later become the ends of the major veins carrying blood to the heart as well as parts of the atria.  The next segments are the primitive atrium and primitive ventricle which will become the atria and ventricles of the adult heart.  Cranial to these segments are the bulbus cordis, most of which will become the right ventricle, and the truncus arteriosus which forms the pulmonary and aortic trunks carrying blood away from the heart.
+'''Trilaminar embryo:''' Term used to describe the early three (3) layered embryo following gastrulation when it now has a structure consisting of the 3 germ cell layers: ectoderm, mesoderm, endoderm. In humans, this developmental stage occurs during week 3. Do not confuse the term "germ cell layers" with "germ cells", which refer to the egg and sperm.
-===Heart Tube Looping===
+'''Ventral:''' Anatomical term referring to structures that are more towards the front.
-This tubular heart undergoes a process of looping during week four of development to form a shape that resembles that of the adult heart.  It initially forms a C-shape (with the convex portion of the C situated on the right side of the embryo) and then an S-shape.  Eventually the atria are brought backwards and upwards, so that they lie cranially and behind the ventricles.
+[[category:heart]]