Internal Features of the heart Flashcards
Describe the process of heart formation
1) Two endothelial primitive tubes, which will unite to form one tube having a venous end (where the blood enters) and an arterial end (where the blood exits)
2) The joined tube will then undergo the first constriction forming a primitive ventricle (PV) on the top & a primitive atria (PA) at the bottom
3) More constrictions will occur forming a sinus venous, primitive atria, primitive ventricle, bulbus cordis (BC), and truncus arteriosus (from bottom to top)
- Primitive atria and ventricle will then have a septa that divide them into right and left
Describe the external features of the right atrium
- It forms the right surface and border of the heart
- An auricle projects from the anterior upper angle of the right atrium, covering the right side of the root of the pulmonary trunk with its rough inner surface
- Its lateral wall has cristae terminalis (ridge) on the inside cavity, which is correspondent to the sulcus terminalis groove (extends from the opening of the superior vena cava till the opening of the inferior vena cava) on the outside
What is the anatomical significance of the cristae terminalis?
- It divides the anterior part of the right atrium into the rough anterior part (contains the musculi pectinate), the Smooth posterior part (where the opening of the veins brings the blood “SVC, IVC, & the Coronary Sinus), and the septal part which separates the right atrium from the left
What is the clinical importance of the musculi pectinate found in the cavity of the right atrium?
During blood disturbance, this area is most prone to developing clots
The opening of the SVC is at the level with which costal cartilage?
Right third costal cartilage
At which vertebral segment is the IVC?
Sixth thoracic vertebrae
Describe the structure of the interior of the right atrium
1) Anterior rough part (Atrium Proper)
- Consists of the pectinate muscles that runs from the cristae terminalis
- Derived from the right 1/2 of the atrial chamber of the primitive heart tube
2) Posterior smooth part (sinus venarum)
- Contains the opening of the SVC, IVC, & Coronary Sinus
- Derived from the sinus venosus
3) Septal wall
- Formed by the inter-atrial septum
- Fossa Ovalis (oval depression representing the septum primum of the fetus)
- Annulus ovalis (crescent margin of the fossa ovalis, representing the caudal part of septum secondum)
What are all of the openings of the right atrium and what is their relation to other body parts?
1) Opening of the SVC:
- 3rd costal cartilage, has no valves
2) Inferior Vena Cava:
- 6th costal cartilage, has a valve
3) Coronary sinus opening:
- Between the opening of the IVC & the tricuspid orifice
- Guarded by the coronary sinus valve
4) 3 or 4 Opening for the anterior cardiac veins
5) Venae Cordis Minimi:
- A lot of small veins that open into the atria
Describe the blood flow in the fetal atria
At the beginning of life, there is an opening between the right atrium and left atrium which is called the foramen ovale
1) first the interatrial septum develops as two layers the first one being the septum premium which goes to join the septum intermedium, at first it before it joins the septum intermedium it has an opening called the foramen premium
2) Then once the septum premium joins with the septum intermedium the foramen ovale will appear via apoptotic activity
3) On the right side of the heart a second septum will start forming called the septum secondum which will cover but not completely the foramen ovale opening in the right atrium
4) After birth due to the increased pressure in the LA and decreased pressure in the RA the two septa will stick on together closing
- Once the foramen ovale is closed the septum secondum will form the annulus ovalis and the depression formed by the septum premium is the fossa ovalis
Describe the internal features of the left atrium
- Consists of a main smooth cavity with four openings for the pulmonary veins and an auricle with a rough surface
- Forms most of the base of the heart, with a thicker wall compared to the RA
- It has a mitral orifice, vena cordis minimi orifices, & the orifice of the four pulmonary veins
- The fibrous pericardium separates it from the esophagus
Which parts of the heart are formed by the right ventricle?
1) Most of the sternocostal surface
2) 2/3 of the inferior border of the heart
3) right 1/3 of the diaphragmatic surface
Describe the internal features of the heart
- It has a rough inflowing part and a smooth outflowing part, separated by the supraventricular crest which extends between the tricuspid and pulmonary orifices
Rough Inflowing Part:
1) The trabeculae carnea from its rough wall, has three projections which are the papillary muscles that are attached to the tricuspid valve via the Corda tendinae
2) The three papillary muscles are the ANTERIOR, POSTERIOR & SEPTAL (each is connected to its corresponding cusp “same same name regarding the cusp “valve”)
3) Has a Moderator band “septomarginal trabeculae” which extends obliquely, preventing the over extension of the ventricle
Smooth Outflowing Part:
1) Lies above the supraventricular crest
2) Smooth conical shape named as the “INFUDIBULUM”
3) The Infundibulum (conus arteriosus) is formed from the bulbus cordis which is separated into the anterior “INFUNDEBULUM” & posterior “VESTIBULE IN LV” which leads to the pulmonary trunk formed by the TRUNCUS ARTERIOSIS
What are the external features of the LA?
It forms:
1) The apex of the heart
2) Most of the left surface along with the left auricle
3) Left 1/3 of the sternocostal surface
4) Left 2/3 of the diaphragmatic surface
- Its walls are 3 times thicker than those of the right ventricle, and it is circular in shape
Describe the internal features of the left ventricle
1) Rough Inflowing Part
- Extends from the left atrioventricular orifice to the apex of the heart
- It has trabeculae carnea (more than the right ventricle), which has projections called the papillary muscle (anterior and posterior)
2) Smooth Outflowing Part
- It has the AORTIC VESTIBULE formed by the bulbous cordis, the aortic vestibule is composed of FIBROUS tissue
Why is the aortic vestibule composed of fibrous tissue?
To remain patent all the time, and we don’t want it to be liable to collapse
