Heart, Blood, Lung Development Flashcards
Heart:
1. role in CVS
2. function
3. fatigue
- positive displacement pump, fill during diastole and eect blood during systole
- pump blood with oxygen and nutrients to body
- cardiomyocytes are highly resistant to fatigue
Heart development at 18-21 days
- overview
- comp of mesoderm
- cranial-caudal folding
- differentiation of the lateral plate
- fusion
- rapid dev of cardiac tissue
- paraxial, intermediate, and lateral plate each with a splanchnic and somatic portion
- at 18 days embryonic folding brings the heart from head to cardiogenic region
- VEGF expression promotes differentiation of lat plate splanchnic portion into cardiogenic tissue forming pericardial coelom/cavity, angioblasts (BV) form endocardial tubes, and hemocytoblasts form BC
- endocardial tubes fuse (20 days) with the endoderm and pericardial coelom to form a primitive heart tube in pericardial cavity at 21 days
Heart dev at 22 days:
1. location of primitive heart
2. layers of the heart tube
3. regions of the heart tube
4. contractions
- center of the pericardial cavity anchored by dorsal mesocardium
- myocardium (myocytes) superficial and endocardium (endothelial cells)
- truncus arteriosus (pulm trunk and asc aorta), bulbus cordis (RV and outflow tracts), primitive ventricle (LV), primitive atria (R/LA), sinus venosus (IVC, SVC, coronary sinus, and conduction sys
- begin pumping blood from sinus venosus to truncus arteriosus
Heart dev at 23-35 days:
1. bending of tubes
2. cardiac looping
- 23 days, truncus arteriosus and bulbus cordis fold down and left, primitive ventricle and atrium fold up and left, day 24 is S-shape
- 35 days, primitive atrium wrap around truncus arteriosus, forming L/RA, primitive ventricle become LV, bulbus cordis becomes RV
Heart dev 28 days-8 weeks:
1. partitioning
2. complete separation
- atrioventricular canal dev to separate atria and ventricles, septum primum form b/w atria, interventricular septum begin forming
- septum secondum and septum primum leave a hole called foramen ovale to allow bypassing pulm circ, interventricular septum close off ventricles, chordae tendineae and AV values form
fetal circulation:
1. placenta
2. ductus venosus
3. ductus arteriosus
- site of gas exchange in fetus
- O2 rich blood from placenta to RA
- allow O2 rich blood to bypass pulm circ due to high pressure in RV due to hypoxic vasoconstriction to aorta by connecting it to pulm vein
Placental gas exchange:
1. struc
2. maternal > fetal
3. fetal > maternal
- maternal blood pools into lacunae in intervillous spaces with chorionic villi that facilitate nutrient and gas exchange
- O2, nutrients, vitamins, antibodies, and H2O diffuse from lacunae to fetal capillaries
- CO2, urea, and hormones diffuse from lacunae to maternal BV
Neonatal circ changes
- filling of lungs at birth changes pressure grad b/w L/RA to close foramen ovale into fossa ovalis
- ductus arteriosus and venosus close and become ligamentum arteriosum/venosum to allow blood to pass through pulm circ as lungs become site of gas exchange
- increase BF to lungs and decrease mixed blood
fetal blood:
1. fetal blood content
2. function of 2,3 disphosphoglycerate
3. fetal hemoglobin
- 20% higher hematocrit than mother for higher O2 carrying capacity
- neg-charged allosteric effector that binds to hgb to lower O2 affinity for greater offloading of O2 at tissues
- decreased affinity for 2,3 DPG thus has higher O2 affinity than adult hgb
oxyhemoglobin dissociation curve:
1. function
2. shift left/right
3. changes
3. fetal oxyhemoglobin curve
- shows relation b/w O2 saturation of hgb and partial pressure of O2
- shift left for increased affinity, shift right for increased offloading
- increase temp and 2,3 DPG and decreased H+ shift right, increased PO2 shift left
- more left because less 2,3 DPG for higher )2 affinity to transfer O2 from mother to fetus in hypoxic environment
Lung dev overview:
1. comp
2. 5 stages of lung dev
3. folding
- endoderm forming epithelial lining of resp tract and splanchnic portion of lat plate mesoderm form cartilage, BV, CT, and muscle of resp sys
- embryonic, pseudoglandular, canilicular, saccular, alveolar
- lat and cranial-caudual fold at same time, lungs bud off esophagus of foregut to form respiratory diverticulum (lung bud) with splanchnic LP surrounding it
embryonic stage of lung dev
week 4 forms resp diverticulum off splanchnic mesoderm, 2 bronchial buds off lung to become bronchi, lung bud partition from esophagus to form separate tubes, endoderm invades trachea to become epithelial lining
pseudoglandular stage of lung dev
5th-16th week
1. bronchi divide, est new airway gen until gen 23 (primary, secondary, tertiary, terminal bronchioles) forming L upper and lower lobes and R upper, middle, lower lobes
2. splanchnic LPM encircles bronchioles for budding
3. no respiratory bronchioles yet
canalicular stage of lung dev
week 16-25, func lung dev
1. vascularization and formation of resp zones (where gas exchange occurs; comp resp bronchioles, alveolar ducts, primitive alveoli)
2. inner surface of alveoli lined with cuboidal cells that req differentiation to facilitate gas exchange
saccular stage of lung dev + Laplace’s law
week 26-birth
1. increase number of pulm capillaries, alveoli, and resp bronchioles
2. maturation of alveoli, differentiation of cuboidal cells into type I (squamous, gas exchange) and II pneumocytes (produce surfactant)
3. surfactant reduces surface tension caused by air-water interface via amphiphilic properties to exert force against H2O compression to prevent atelectasis (alveolar collapse)
4. Collasping pressure (P) = 2T(tension)/r
