Chapter 9 Resp Development Flashcards
1
Q
Primary purpose of the respiratory system is to preform ?
A
Gas exchange
2
Q
What happen during the process of gas exchange?
A
Gas exchange supplies the oxygen that cells need to produce ATP, It also removes the carbon dioxide produced during aerobic glycolysis.
3
Q
External Respiration
A
Diffusion of alveolar gas across the A/C membrane.
4
Q
Internal Respiration
A
Diffusion of oxygen and carbon dioxide across the capillary wall at the level of the tissue cells
5
Q
Ventilation
A
Mechanical process of moving air in and out of the alveoli either spontaneously or with assisted ventilation.
6
Q
Diffusion
A
Process by which gases move across biologic membranes ( A/C Membrane in the lung, and the capillary and cell membranes at the tissues.
7
Q
Three meaning of Respiration?
A
External resp. Internal respiration. Respiration
8
Q
Respiration refers?
A
Intracellular metabolic process of converting the energy stored in the nutrients of the useable energy in the form of ATP in the mitochondria.
9
Q
In the embryonic period ( the first 6-8 weeks), all the body’s major organ begin to develop from the three PRIMARY (derm) layers
A
Ectoderm, Mesoderm, and endoderm
10
Q
After conception, the Pulmonary system develops
A
About 3 week after conception, in the Embryonic period and continues through the fetal period up to birth.
11
Q
The Carnegie stages are a system that embryologists use to describe
A
the apparent maturity of the embryo during the first 8 weeks (56 days) after conception
12
Q
During intrauterine life.. ( when a fertilized egg implants and grows in the correct place) ,
A
the developing lungs are fluid filled organs that do not perform ventilation
(breathing) or gas exchange.
By delivery, the lungs must be sufficiently developed so they can immediately perform ventilation and
gas exchange within seconds after birth
13
Q
At birth, the human pulmonary system makes a remarkable transition
A
from a fluid filled non-gas exchange
structure to the fluid lined gas exchange structure it will remain for life.
14
Q
Lung development is divided into five stages
A
embryonic(0-10 weeks) ,pseudoglandular (5-20 weeks), canalicular (15-30 weeks), saccular (25-40 weeks), and alveola (30-40 week)
15
Q
How long is the lung growth continues after birth ?
A
into the eighth or tenth year of life.
16
Q
Fertilization takes place in a section of the oviduct (fallopian tube) called
A
ampulla, which curves over the ovary.
17
Q
Diploid (two complete sets of chromosomes in an organism’s cell)
A
most of their cells contain 23 chromosomes 23 pairs
from the father and 23 from the mother
18
Q
How does the embryo take to reach the Lumen of the uterus?
A
It takes the embryo (the fertilized egg cell) about 5 days to reach the lumen of the uterus
19
Q
During its 5-day journey of the embryo?
A
the zygote (the terms embryo and zygote are usually interchangeable)
undergoes mitotic divisions called cleavage divisions
20
Q
cleavage divisions
A
This mitosis occurs without producing and
daughter cells.
* The cells now form a hollow sphere called a
blastocyst.
* When the embryo reaches the 8-cell stage, it
changes from a loosely organized ball of cells
by the process of compaction
21
Q
Process of compaction
A
Compaction creates two cell lines:
1. The trophoblasts which form a portion of the placenta; and
2. The inner cell mass which forms the embryo itself and the
extraembryonic membranes
22
Q
extraembryonic membranes
A
The amniotic membrane of the amniotic cavity and the
extraembryonic mesoderm [EEM]
o The EEM contributes to the formation
Once it arrives in the uterus, the embryo and the uterine lining recognize each other
biochemically.
* This recognition allows the embryo attach to the uterine wall.
* Attachment is followed by implantation
23
Q
At implantation
A
the inner cell mass reorganizes into a two layered embryo; called the
epithelial epiblast, which will form the embryo the amniotic membrane and the
hypoblast.The amniotic cavity appears on about day 8 as fluid collects between epiblastic cells facing the trophoblasts
24
Q
amniotic epithelium
A
The cells delaminate (divides) and differentiate (a process called organogenesis). This will eventually form the amniotic membrane and the amniotic cavity that
will surround
25
Between the 14th and 18th days after
conception, the process of
gastrulation starts, Gastrulation produces the three germ layers that will develop into the tissues and organs of the fetus. Think of the fetus as
developing from a three-layered tub.Three primary germ layers,The ectoderm. The mesoderm.The endoderm. The germ layers contain the cells that will
develop into the tissues and organs of the developing fetus
26
The ectoderm (the outside of the tube)
produces the skin and the nervous system tissues.
27
The endoderm (the inside of the tube)
produces the digestive tract and respiratory tract
tissues
28
The mesoderm (in-between the outside and the inside of the tube)
produce the cardiovascular, skeletal, and muscle tissues
29
The germinal period runs from
zero(fertilization of the egg) to about two weeks.
30
The embryonic period starts ?
starts with fertilization of the egg and continues for 3 to 8
weeks (56 days).
31
By the eighth week, the embryo is called?
a fetus.
32
The period of fetal growth, the fetal period runs?
from the eighth or ninth week until birth.
33
The Carnegie Stages are a standardized system
assessing fetal development. Base on appearance
34
Assessment of the 23 stages embryo development is based on?
the physical appearance of the development of fetal body
structures. not on body size or the number of gestational days.
Fetal growth from 8-40 weeks
35
Pulmonary development during the fetal period occurs in four stages
Pseudoglandular, Canalicular, Saccular (aka terminal saccular), and Alveolar stages
36
Breathing-like movements (chest expansion and contraction) in the fetal..
begin around the end of the embryonic period.
- The chest-wall movements are controlled by a breathing center in the brain stem
37
By about the 25th week of fetal growth..
the pulmonary capillaries develop and alveolar Type
II pneumocytes are mature enough to begin producing pulmonary surfactant
38
A baby born prior to 37 weeks gestation is classified
classified as premature.
* 24-26 weeks is usually considered the earliest point at which a fetus will be viable (able to
survive) in the extrauterine environment with medical and respiratory support
39
The placenta
The nine by one-inch pancake shaped placenta connects the amniotic sac to the uterus and serves as the interface between the fetal and maternal circulations
-It allows the exchange of nutrients, oxygen, and waste products
between the maternal and fetal circulatory systems
-The placenta also helps to protect the fetus from certain chemical substances in the mother’s blood, some infections, pathogens, and some maternal diseases
-The placenta also releases hormones into both the maternal and fetal circulations to affect pregnancy, metabolism, fetal growth, the birth process (parturition) and other functions
40
The functional units of the placenta are
chorionic villi, which separate fetal and maternal blood.
-Villi penetrate the placenta and form irregular pockets called intervillous spaces.Blood from maternal arterioles enters the intervillous spaces and bathes the fetal chorionic villi.
Branches of the umbilical arteries carry fetal blood to the villi.
- After circulating through the capillaries of the villi, oxygenated blood
returns to the embryo through the umbilical vein.
41
The developing fetus is surrounded
amniotic fluid (AF) in the amniotic sac. The amniotic sac is a bag of fluid inside a pregnant woman's uterus (womb) where the unborn baby develops and grows.
42
The utlrasonograph biophysical profile measure?
The Amniotic Fluid index.
-Also evaluates fetal breathing, body movement, tone, and reactive heart rate.
-predict the presence or absence of fetal asphyxia
-The profile score for normal fetus 8-10 , lower profile indicate significant fetal and newborn problems
43
The amniotic sac is made of two membrane layers
The outermost layer, which lines the uterus, is the chorion.
The inner layer, closer to the fetus is the amnion.
44
When does Amniotic Fluid occur?
AF production begins 12 days after conception when the amniotic sac form.
AF is about 98-99% water, chemical composition changes as pregnancy advances. The water originally a filtrated plasma from the mother's placenta.
45
The complete of Keratinization
(formation of fetal tissue) at about?
25 weeks, the fetal skin is freely permeable to water.
-at 10 weeks AFV is about 25ml
-at 12 weeks, fetal kidneys begin to produce urine.
- at 16 weeks AFV is about 200ml
- at 20 weeks,AFV is about 400ml
- at 20 weeks urine from the fetal kidneys and fetal lung liquid secretions are the major sources of AF.
- at 28 weeks AFV plateaus at about 800ml
- at 32-35 weeks, The AFV levels off at about 780-800ml
- In port term pregnancies (>40-42 weeks) the AFV declines to about 400ml.
46
Amniotic fluid functions
- Cushion protection from injuries
-maintain relatively constant Temp. (37c)
- Allow for fetal movement, which allow muscle and bone growth.
- lubrication, keeps external body parts from growing together.
- if too small, sometime it might cause the finger and toes webbed
- Provide water and nutrients
(carbs, proteins, and lipids )
- Provide Meternal electrolytes, growth hormones, and defensins from the innate immune systems
-Fetal lung liquid and AF in the digestive tract, are essential for proper development of the lungs and GI tract.
47
Functions of AF and fetal Lung liquid
- Decreased fetal lung liquid result is pulmonary Hypoplasia (undeveloped lung)
- Around 11 weeks the fetus, uses resp. muscles to move small amount of AF in and out of the airway, at the same time also swallowing the AF. Urine and fetal lung liquid production balanced by fetal swallowing becomes the main factor that control AF volume
48
Amniotic Fluid appears?
-clear or straw colored.
- AF that is greenish or brown or contains streaks of greenish-black material is called Meconium stained AF
49
Meconium Stained amniotic fluid
Meconium is collection of secretion, desquamated (shedding) cells from the digestive tract and waster product from ingested amniotic fluid. (form beat the start and 2nd trimester, accumulates in the fetus's colon)
-rare prior to 34 weeks
50
Danger of MSAF incidence
Incidence of MSAF is about 13% of birth, indicating that the fetus had passed the meconium in utero
- increase with gestational age at delivery.
-Meconium aspiration syndrome can occur if inhaled into the lung before, during or immediately after birth ( only treatment is selective intubation and suctioning with meconium removal catheter
51
Oligohydramnios
Oligohydramnios aka hydramnios mean too little AF.
- may occur with late pregnancies, ruptured membranes, placental abnormalities, or problems with the fetal kidneys or urinary tract.
-strongly associated with poor lung development, preterm birth, infection ( if ruptures )
52
Polyhydramnios
too much AF
-unk cause, occur 30-60%
-might occur with multiple gestations
-congenital fetal anomalies
- gestational diabetes.
53
Acute Chorioamnionitis
intra-amniotic bacterial infection
Chorion and amnion membranes and the amniotic fluid may be infected.
-usually caused by a bacterial pathogen
54
Amniotic fluid embolism
Normally intact fetal membranes
isolate the amniotic fluid from the maternal circulation.
-small tear in the uterine wall during delivery potential portal entry for AF into maternal circulation.
-Pressure gradient may develop between the AF and maternal blood
-AF contain powerful vasoconstrictor and other element that may cause acute pulmonary hypertension follow by right and left ventricular failure and death.
55
Amniotic band syndrome
cause by strands of amniotic sac that separate and entangle digits, limbs, or other parts.
-lead to fetal death or malformed or severed limbs
-degree of harm depends on where the strand s is located.
56
During fetal lung development
fetus does use the lungs to breathe
-fetal blood is low is oxygen hemoglobin saturation is only 70-80%
- maximizes oxygenation to the brain, heart, and other vital organs by bypassing lung and liver .
57
Fetal cardiovascular system uses three shunts for this bypass
-The ductus venosus, 50% of the left umbilical vein blood past the liver into the inferior vena cava
-The foramen ovale, diverts blood from the right atrium to the left atrium
- The ductus arterious, diverts blood from the pulmonary artery to the descending aorta.
58
Gas exchange in the fetus occurs
palcenta, not in the lungs.
59
Fetal get oxygenated and nutrient rich blood from
From the mother's uterine artery flows into the intervillous spaces in the placenta
- Meternal blood in the placenta has a PO2 of 50mmhhg
- Fetal umbilical arterial blood has PO2 of 19mmhg
gradient of 02 diffuse into the fetal capillaries and enter the umbilical vein is 50mmhg-19mmhg = 31mmhg.
60
Fetal capillaries in the villi on the fetal side of the placenta
pick up oxygen and nutrients from the maternal blood according to this gradient.
61
fetal Umbilical vein
merge of fetal capillaries.
- carries oxygenated blood from the gas exchange structure (placenta)
- Umbilical arteries carry deoxygenated from the heart back to the placenta
-Umbilical venous blood has highest oxygen level.
-Since the PO2 of fetal blood is low, circulation is designed to send the highest oxygenated blood to most important organs: the coronary circulation to nourish the myocardium and the cerebral circulation for the brain.
62
Deoxygenated fetal blood returns to the placenta through
two umbilical arteries.
-The fetal circulation can do this because it has three bypass pathways
1. foramen ovale (intracardiac shunt)
2. ductus venosus( extracardiac shunt)
3. ductus arteriosus (extracardiac shunt)
63
Fetal blood is oxygenated in ?
the fetal placental capillaries and flow through the single Umbilical vein to the fetal heart.
64
Pathway of blood flow in the fetal Circulation.
1. ~ 40% flows to the fetuses’ liver.
▪ That 40% perfuses the liver through the hepatic circulation.
▪ The other 60% goes through the first shunt, the ductus venosus (blood in the
duct is called ductal blood).
2. Ductal blood flows into the inferior vena cava (IVC) where a fascinating example
of physics and physiology occurs:
* The oxygenated blood from the UV tends to stream (flow) along the
posterior (dorsal) wall of the IVC.
* While the deoxygenated blood from the lower torso and the liver streams
along the anterior (ventral) wall of the IVC.
* Streaming prevents the oxygenated and deoxygenated blood from mixing.
* Blood in the IVC drains into the right atrium where it splits into two parallel circuits:
1. Into the right ventricle and then into the pulmonary circulation.
* The blood then flows into the left atrium and the left ventricle.
* The foramen ovale is the intracardiac shunt in the septum between the left
and right atria (Latin plural of atrium).
2. Into the systemic circulation via the ductus arteriosus.
* The ductus arteriosus connects the pulmonary trunk to the proximal
descending aorta.
From the left ventricle
through the second shunt, the foramen ovale, into the left atrium.
o The foramen ovale is an opening in the septum between the right and left atria.
o A small tissue flap in the superior portion of the inferior vena cava (IVC) called
the Eustachian valve, directs the oxygenated blood from the IVC toward the
foramen ovale.
* Left atrial blood goes through the mitral valve into the left ventricle and into the
ascending aorta.
1. Ascending aorta blood supplies oxygen to the upper body, especially the brain
and the heart muscle (myocardium).
2. Blood for the lower body comes from the combined output of the left ventricle
and the right ventricle via the ductus arteriosus.
* Deoxygenated blood from the lower torso and the hepatic circulation streaming along the
anterior wall of the IVC.
1. During fetal life, oxygenated blood from the placenta and deoxygenated blood
from the liver and the lower torso both flow through the inferior vena cava (IVC).
2. The differential streaming (see above) prevents the oxygenated and deoxygenated
blood from mixing.
3. The deoxygenated IVC blood flows through the tricuspid valve into the right
ventricle then into the pulmonary artery and into the pulmonary vasculature.
* Fetal alveoli are fluid filled and are thus hypoxic.
* Alveolar hypoxia causes pulmonary vascular resistance (PVR) to be very
high.
* Because of the fetus’s high PVR only about 10-12% of the right ventricle output is able
to flow into the pulmonary vasculature.
* The other 88% of the right ventricular output crosses the third shunt, the ductus
arteriosus into the descending aorta.
1. Descending aorta blood supplies the lower half of the body with the small amount
of oxygen it needs.
* This blood then enters the umbilical arteries and flows back to the placenta where CO2
and other wastes are released and fresh O2 is picked up.
65
The Pseudoglandular stage
-Runs from about 6 or 7 to the 16th week of the fetal period.
-this stage the developing lung resembles a hollow tube-like (glandular) structure surrounded bu mesenchymal cells.
66
The develop of the primitive bronchial tree during the Pseudoglandular stage
- the bronchial tree is initially lined with cuboidal epithelial cells that will differentiate into ciliated epithelial and mucus secreting goblet cells.
- the first ciliated epithelial cells can be found by the 8th to 13th week of pregnancy.
67
The first type ll pneumocytes (synthesizing cells of the alveolar surfactant) begins
During the Pseudoglandular stage, the type ll pneumocytes begin lining the areas that will become the gas exchange (parenchymal) surface
- irregular dichotomous branching growth continues
- All airway divisions are essentially complete by 16 weeks of gestation.
68
Terminal bronchioles are ?
-the most distal branches
- begins to differentiate to form respiratory bronchioles and alveolar ducts.
69
Development of airway Cartilage
begin to form around the larger airways and smooth muscle forms around both airways and major blood vessels.
70
During the Pseudoglandular stage, developing broncho-pulmonary epithelium
-Also begins to produce fetal lung liquid ( surfactant )
-essential to normal pulmonary development
-Some of the liquid is expelled from the mouth and becomes part of the amniotic fluid
71
During fetal development, the lung is
liquid filled none gas exchange organ.
72
Fetal lung liquid is vital to
-growth and development of the lungs by keeping them in a distended state, which stimulated their growth.
-Inadequate fetal lungs growth occurs because of a reduced volume of fetal lung liquid.
73
The volume of fetal lung liquid is principally regulated by a balance between two factors :
- high resistance to liquid efflux through the narrow fetal upper airway (trachea)
-The respiratory muscles activity that produces fetal breathing movements(FBM)
74
The fetal diaphragm makes..
periodic respiratory like movement, which move a small tidal volume of liquid back and forth in the airway
-during episodes FBM, the larynx is actively dilated. Reduces airway resistance and allows increased lung liquid efflux ( flow outward)
75
During periods of no FBM
The relatively high resistance of the upper airway reduces lung liquid efflux
76
Successful transition from intra-uterine to extra-uterine life depends on the clearance of the fetal lung liquid at the time of birth; three events must occur
1. Absorption by the fetal lung
2. bulk removal during vaginal delivery
3. development of pulmonary surfactant
77
Mesenchymal cells make up
loosely organized, mainly mesodermal embryonic tissue which develops into connective and skeletal tissues.
- the loose nature of the cells allow the tissues to move and be molded
-During embryogenesis, mesenchyme gives rise to the body's connective tissues, from cartilage and bone to fat, muscle and to the circulatory system and blood and lymph.
78
The canalicular stage
occur 16th -24th or 26th weeks
-canaliculi (canals) start to branch out from the terminal bronchioles
- The canaliculi will develop into the actual respiratory (gas exchange or parenchynmal) tissue of the lungs
79
All the Alveoli that develops?
From a single terminal bronchiole form a parenchymal until called an acinus (terminal respiratory until)
- each acinus consists of the respiratory bronchioles alveolar ducts and (after further development ) the alveolar sacs that branch from a single terminal bronchiole
80
The chief characteristic of this phase (canalicular stage) is
the alteration of the epithelium and the mesenchyma surrounds the air spaces
- capillaries begin to invade the mesenchyma along the acinus.
- the capillaries will eventually surround the acini in a dense layer and will make gas exchange possible.
- The lumena (open diameter ) of the canals become wider and the epithelial cells begin to get flatter.
- the cuboidal type ll pneumocytes are the cells that develop into the flattened type l pneumocyctes
81
By the 24th week of pregnancy of the canalicular stage
enough type ll pneumocytes have differentiated into the type l pneumocytes and enough capillaries have proliferated into the mesenchyma to allow the fetus to survive outside the uterus with supplemental oxygen, support of ventilation and surfactant administration.
82
Alveoli are gas exchange sacs lined
by squamous Alveolar type 1 (AT1) cells and cuboidal, surfactant-secreting Alveolar type ll (AT2) cells
-1. There is a switch after birth, when AT2 cells function as stem cells that
contribute to alveolar renewal and repair.
2. However, the AT2 cell growth signal (EGFR-Kras1) can also control the
development of cancer.
- 1All human cells contain a gene called KRAS that serves as a key regulator of signaling
pathways responsible for cell proliferation, differentiation, and cell survival. If a
mutation occurs in a KRAS gene, it may allow cells to multiply out of control, which can
cause cancer.
83
Saccular stage
about 26th weeks to birth, the most peripheral air spaces look like sacs, importantly the interstitial material is compressed to reduce the distance between capillary blood and alveolar air
- Alveoli start to separate as mesenchymal ridge (crests) grow to from septa between sacs
- Cuboidal epithelial cells differentiate into the rounded secretory type ll pneumocytes and the squamous(flatter ) epithelial type l pneumocytes.
-the type ll cells develop lamellar bodies that makes and store pulmonary surfactant. ( surfactant has a half life of about 14 hours, so it must be continuously synthesized
-type ll pneumocytes are also able to differentiate into type l cells to help repair lung injury.
84
Septa
-skeleton of fine collagen and elastin fibers, smooth muscles cell precursor
- as the new septa grows, 1 of the 2 layers of the capillary network of the preexisting septa begin to fold up
-as the septa folds up, it begin to subdivide the preexisting air spaces and new alveoli are created. the preexisting and newly formed septa still contain a double-layered capillary (microvascular) network.
-the next phase of microvascular maturation can take from 0-3 yrs as the capillary layers fuse and form a dense layer of capillaries surrounding the alveoli.
85
Pulmonary surfactant
Pulmonary surfactant is a phospholipid protein consisting of about 90% lipids (fat) and 10% protein
- The prodominant phospholipids are
Dipalmitoylphosphatidylcholine (DPPC) which is a phospholipid and a lecithin.
-DPPC makes up about 50% of the lipids and is the major component of pulmonary surfactant.
- Phosphatidylglycerol (PG) and phosphatidylcholine (PC) are also prominent lipids in surfactant. PG is generically called lecithin.
-Sphingomyelin and phosphatidylinositol also make
up part of the lipid concentration.
* There are four surfactant proteins (SP) named SP-A,
SP-B, SP-C, and SP-D
- The surfactant protein interact with the lipids to produce the metabolic (immune) and physical (surface tension lowering) effect of surfactant.
- By 34 weeks of gestation, most infant produced enough surfactant to be able to prevent lung collapse.
86
Amniotic fluid can be aspirated
by a procedure called amniocentesis.
-levels of the surfactant components lecithin, sphingomyelin and phosphatidyglycerol can be measured.
- a ratio between lecithin and sphingomyelin of >2 indicates alveolar type ll pneumocyte maturity ( low risk for infant respiratory distress syndrome
- an L/S ratio <1.5 indicates inadequate surfactant levels and HIGH IRDS risk.
87
Surfactant performs at least two important functions in the lungs
Its a chemical structure allows it to act as a biophysical agent that modifies surface tension forces at the alveolar air/water interface (physical action)
- the biophysical action helps to prevent alveolar collapse at the end of expiration.
- surfactant helps prevent collapse especially of the smaller alveoli
-physiologists refer to preventing such collapse as stabilizing different size alveoli
88
Pulmonary surfactant is also an import component of the lung's immune response ( metabolic action )
- surfactant helps to keep the distal airways and lung parenchyma clinically sterile
- SP-A and SP-D proteins damage pathogen membranes and regulate the inflammatory responses of alveolar macrophages
-SP-A and SP-D proteins are referred to as pulmonary collectins
- The immune function of surfactant proteins is to help damage the cell membranes of pathogen and to regulate phaocytosis and the inflammatory responses of alveolar macrophages
89
Alveolar stage
Alveolar stage begins at about 32 weeks, Alveolar development continues into the 8th or 10th years of life.
90
Formation of alveoli
Formation of the hexagonal alveoli is closely linked to formation of the structural protein ELASTIN.
- The alveoli become invaginated (enclosed in a sheath of tissue) by epithelial cells bulging from sac wall
-the epithelial cells form crests to form the alveolar septa that separate individual alveoli which greatly increase the surface area for gas exchange
- The alveolar epithelium and the capillary endothelium rest on top of basement membranes and are fused to virtually form a single structure. This makes A/C gas exchange barrier very thin (<0.5 microns)
91
The Amount of alveoli
A full-term neonate has about 50 million alveoli providing a gas exchange surface area of about 3 - 4 m2
- by two years old alveoli have reached the adult number of about 300 million,
adult range of 270 to 790 with 480 million by age 8 to 10
- Adult lung has a gas exchange surface area between 50-100 m2
92
Before birth , the fetus's gas exchange organ is
the mother's placenta.
93
At birth, the fetus makes the transition to a neonate breathing air. several events occurs at that transition:
-Several days before birth the fetal lung epithelium stop producing alveolar lung fluid.
-The fluid begins to be reabsorbed by the fetal pulmonary capillaries.
- During vaginal delivery about one third of the remaining fetal lung liquid is squeezed out of the lungs by compression of the thorax during passage through the birth canal.
94
At fetus delivery
Placental blood flow stops at delivery, the infant becomes increasingly hypoxic and after about 10 second the infant gasps.
-First gasping breath followed by crying is initiated by central neurologic stimulation secondary to arousal by sound, light, temperature change and touch
-central chemoreceptor cells in the medulla signal the respiratory muscles to work in response to receptor stimulation by acidemia and hypercarbia (high co2 in the blood)
95
The baby must generate very high negative inspiratory pressure during the first few breaths to overcome:
-High airway resistance due to the remaining viscous fluid in the airways
-High inertia of viscous fluid in the airway
-High alveolar surface tension because of the remaining fetal lung liquid in the alveoli
96
As the baby exerts muscle strength to distend the alveoli the adrenal gland is stimulated to release the hormones cortisol and epinephrine
Cortisol is a stress hormone that increase blood sugar through gluconeogenesis, this provide glucose for ATP production.
Epinephrine produces a number of responses, including airway dilation which reduces airway resistance.
-Alveolar distention also stimulates the type ll pneumocytes to produce pulmonary surfactant which help reduce surface tension.
97
To survive outside the urterus, the fetal pulmonary and cardio vascular systems have to make a drastic changes within second, these change includes
The first breath, it helps clear the remaining fetal lung liquid.
-each inspiration moves lung liquid from the airways into the distal airspaces (alveoli) where it then moves across the alveolar wall into the pulmonary interstitium.
- aerates ( introduce air into) the lungs and established the FRC, Crying help maintain the FRC.
98
Pulmonary interstitium
Is the space between the alveolar wall and the pulmonary capillary
-lymphatic channels in the interstitium return the fluid to the circulation.
99
Stretching and clamping the umbilical cord does the following:
stopping placental oxygenation greatly increases the systemic vascular resistance (SVR)
-the increased SVR directs the right ventricular cardiac output into the pulmonary circulation instead of the systemic circulation.
- this increase pressure in the left atrium which pushes the Eustachian.
- in a vaginal birth, about one third of the liquid is squeezed of during passage through the birth canal.
the remaining fluid is cleared during the newborn's breathing.
100
The first inspiration of a newborn requires enough muscles effort to
produce a high subambient ( neg) pressure in the Intrapleural space.
- this low intrapleural pressure generates a transpulmonary pressure (Ptp) gradient between intrapleural space and the alveoli of 60cm H20
The high-pressure difference (gradient) is necessary to overcome the effect of high surface tension in the neonate's alveoli.
-A neonate needs to produce a trans plural pressure (Ptp) of 60 cm H20 for the first breath in order to increase lung volume by 40ml
- A healthy adult only needs to change Ptp by 2.5 cm H20 produce a resting tidal volume of 500ml.
101
Premature Lung tissue, not effective for gas exchange :
- Acinar (a small saclike cavity) development is not complete
-the blood/gas barrier is thick
-the lung has low compliance
-epithelial cells are immature
-surfactant levels are too low to prevent alveolar collapse
-there is a small are for gas exchange
-the lung is poorly vascularized
-there is high resistance to blood flow
102
Mature Lung tissue , effective for gas exchange:
-Acinar development is complete
-the blood / gas barrier is thin
-the lung is highly compliant
-epithelial cells are mature
-surfactant levels are adequate to prevent alveolar collapse
-there is a large area for gas exchange
- the lung is highly vascularzied
-there is low resistance to blood flow
