Lecture 3-Exam 2 Flashcards
(107 cards)
1
Q
What does the human development start with?
A
- Starts with fertilization- sperm + oocyte (egg cell) fuse to form a zygote
2
Q
- Seman contains what that enters the vagina?
- Seminal fluid is what?
A
- Semen containing 200 million spermatozoa (sperm) enters the vagina
- Seminal fluid is alkaline which neturalizes the acidic vagina
3
Q
How does the sperm travel in the female reproductive system?
A
- Sperm enters the cervix ->uterus->fallopian tubes ->adjacent to ovary
4
Q
Most of the 200 million sperm that enters the body die via what? (3)
A
- Stuck in vaginal mucous
- Lost in cervix
- WBC’s
5
Q
While sperm wait, they rub against the walls in the tube and does what?
A
to remove the glycoprotein coat and the plamsa membrane off the “head”
6
Q
- What can sperm secrete? What does this do?
A
Sperm can then secrete hyaluronidase which can break down hyaluronic acid (major component protecting the egg)
7
Q
What is sperm binding?
A
The sperm enters the egg through multiple layers and anchors to the surface – they fuse together
8
Q
After the egg and sperm bind, what happens?
A
calcium levels rise which signal enzymes to be released
* The enzymes created a gel like barrier with glycoaminoglycans, water, and calcium called the hyaline layer
* This ensures only one sperm enters the egg….but you could have two and get
twins
9
Q
What is the result in the mature female ovum?
A
While the gel layer is being made, the egg is undergoing cell division, resulting in the mature female ovum
10
Q
- What does the pronucleus of the mature female ovum have?
- The sperm swims to female pronucelus and does what?
A
- The pronucleus of the mature female ovum has 23 chromosomes
- The sperm swims to the female pronucleus and the sperm degenerates into the male pronucleus
11
Q
- The two pronucleus fuse together and release their genetic information, merging into what?
- How does this happen?
A
into a single nucleus
* Mitotic spindle forms and brings chromosomes into complementary pairs aligning them at the center of the cell
12
Q
The cell has both maternal and paternal genetic information. What is this called?
A
a diploid- and is now called a Zygote
13
Q
What are blastomeres?
A
A few hours after the zygote is formed, the new diploid cell is cleaved into a new pair of cells
14
Q
The blastomeres keep splitting into what?
A
4 cells -> 8 cells -> Mulberry shaped 16 cell cluster called a morula with inner and outer cell masses
15
Q
The morula gradualy develops an outer cell mass of what? What does the interior cell cluster filled with?
A
Morula gradually develops an outer cell mass of trophoblast cells and an interior cell cluster with fluid filled cavity at the core called a blastocoel
* At this stage the arrangement of cells is called a Blastocyst
16
Q
The cells making up the inner cell wall of the blastocyst are called what? What will go on to form?
A
The cells making up the inner cell wall of the blastocyst are called the embryoblast because they will go on to form the fetus
17
Q
How are the cells making up the inner cell wall of blastocyte (embryoblast) are arranged how? Trophoblast cells?
A
- They are arranged at one end of the blastocyst in an area called the embryonic pole
- The trophoblast cells flatten into a barrier around the blastocyst called the epithelial wall
18
Q
- Morula means mulberry and is a stage attained when?
- What is each cell capable of doing?
A
- at 3 days with 8-16 cells
- Each cell is capable of forming a complete embryo (totipotent - can give rise to any of the 220 cell types found in an embryo as well as extra-embryonic cells - placenta).
19
Q
What is totipotent?
A
totipotent - can give rise to any of
the 220 cell types found in an embryo as well as extra-embryonic cells - placenta
20
Q
When does compaction begin?
A
Compaction begins when cells on the outside seal themselves from the external environment by forming tight junctions
21
Q
Fluid is pumped toward the inside and begins to displace the inner cells. What happens at this stage?
A
At this stage, outer cells begin to be committed to forming trophoblast (placental) cells, while cells on the inside will form cells for the embryo
22
Q
- When does blastocyst implants?
- Implantation elicits what?
A
6 days, the blastocyst implants
* Implantation elicits an antibody response by the uterine epithelium because the embryo is a foreign body (half its genes come from dad)
23
Q
With the antibody response of the implantation, what does the body normally do? What happens in autoimmune diseases?
A
Normally, the embryo blocks this response, but in autoimmune diseases like systemic lupus erythematosus, the process may not function properly, possibly resulting in infertility
24
Q
- Where does the implantation usually takes place along?
- But, where else could this occur?
A
- Anterior or posterior walls of the uterus
- Ectopic sites
25
What is the most common site for ectopic pregnancy?
The most common site is in the uterine tube, but other sites may occur.
26
What are ectopic pregnancies due to?
Ectopic pregnancies are due to the invasive nature of the trophoblast and abnormal transport or recognition of the blastocyst
27
What is mesentery?
a fold of the peritoneum which attaches the stomach, small intestine, pancreas, spleen, and other organs to the posterior wall of the abdomen
28
Why are ectopic pregnancy dangerous? Why?
They are dangerous because development may proceed for several weeks or months before rupture of the site, including blood vessels, occurs, which can result in severe hemorrhaging and maternal and fetal death
29
What helps the blastocyst implant into the wall of the uterus?
Trophoblast cells
30
Trophoblast cells begin to proliferate and penetrate into the walls, what are these cells called?
* These cells are called syncytiotrophoblast cells
31
The mucousal tissue of the uterus becomes engorged with what and why?
engorged with blood due to the surge of progesterone in the body
32
How long does the blastocyte take to be buried within the uterus lining? What is this now called?
It takes about **11 days** for the blastocyst to be almost buried within the uterus lining – now it is called the **decidua basalis**
33
Placental development continues as the syncytiotrophoblast burrows deeper into the uterine tissue, what is secreted?
human chorionic gonadotropin (hCG)
34
The invasion of the blastocyst is similar to growth of a tumor and can sometimes become unregulated. This results in the formation of what?
Hydatidiform mole
35
HYDATIFORM MOLE:
* Formed from waht?
* Secrete high levels of what?
* May become what?
* What can happen during the earliest stages of development?
* What regulate growth of the embryoblast?
* Formed from trophoblast
* Secrete high levels of hCG (syncytiotrophoblast)
* May become invasive (**choriocarcinomas**)
* During the earliest stages of development, **paternal genes regulate differentiation of the trophoblast (placenta)**
* While **maternal genes regulate growth of the embryoblast**
36
# Development of placenta
What happens around day 14 of development?
* Around day 14 of development, syncytiotrophoblast cells start to form little protrusions called primary villi
* These form around the fetus – at the same time arteries and veins from the mother grow into the decidua basalis to start the creation of the placenta
37
The inner embryoblast cells assemble into two layers forming what?
Embryonic disc
38
What does the ventral and dorsal layers of the disc made up of?
The ventral (underside) layer of the disc is called the **hypoblast**
* Consists of cells that start to line the fluid filled cavity containing the embryoblast cells (**becomes the yolk sac**)
* The fluid is called **vitelline fluid** which washes across the embryo and nourishes it during the early stage
The dorsal layer of the disc is called the **epiblast** and gives rise to all three of the germ layers of the embryo
* **Endoderm, mesoderm, and ectoderm**
39
What does ectoderm, mesoderm, endoderm turn into?
* **Ectoderm**: skin, CNS, PNS, eyes, internal ear, neural crest cells (bones and connective
tissue of the face and part of the skull)
* **Mesoderm**: bones, connective tissue, urogenital system, cardiovascular system
* **Endoderm**: gut and gut derivatives (liver, pancreas, lungs, etc.)
40
* When does gastrulation happen?
* What do the cells of the blastocyst become what?
* Next up is **Gastrulation** which happens around **day 14**
* The cells of the blastocyst become reorganized significantly and they are now a **gastrula**
41
What does gastrulation begin with? How does this happen? The groove defines what?
**Gastrulation begins with the formation of the primitive groove (primitive streak)**
* Starts near the tail (**caudal end**) and grows toward the head (**cranial end**)
* This groove defines the cranial-caudal axis and represent the first instance of bilateral symmetry – a left and right side to the body
42
What is situs inversus?
Situs inversus is a complete reversal of the organs and sidedness, which is not usually a problem clinically. Individuals with situs inversus typically do not have other abnormalities
43
What is kartagener syndrome?
problem with abnormal cilia function. Thus, their situs inversus probably relates to a cilia
problem at the beginning of the third week when cilia in the node should have swept nodal to the left side
* As each organ is formed, it too expresses the cascade of genes that regulates sidedness, for example when the heart loops or the liver or spleen is formed
* People whose organs do not express this cascade properly have laterality sequences in which **one or more organs are on the wrong side but not all of them.** (They do not have complete situs inversus.)
* They also have a **higher chance of having other congenital malformations** (unlike people with complete situs inversus).
44
* Gastrulation transforms the embryonic disc from a bilaminar structure to what?
* When does it begin?
* Gastrulation transforms the embryonic disc from a bilaminar structure to a trilaminar structure
* Gastrulation begins when cells of the epiblast proliferate and migrate toward the primitive streak
45
The result of gastrulation is formation of a trilaminar embryo, and the three layers are called what?
the germ layers because they will “germinate” all of the tissues and organs of the embryo
46
What do the three layers include and what are they formed from?
* The three layers include **ectoderm**, formed from cells that remain in the epiblast
* **Mesoderm**, formed from cells that migrate in through the primitive streak to form
the middle germ layer, including the prechordal plate and notochord
* **Endoderm**, formed by cells migrating through the streak and displacing the hypoblast cells.
47
Gastrulation progresses how? What happens?
Gastrulation progresses in a cranial to caudal direction. Thus, the head region becomes trilaminar first, then the neck, thorax, and so on down the body axis
48
What happens if gastrulation stops too early or too long?
49
At what weeks is the dangerous period for development?
3-8 weeks
50
* During the embryonic period, 3-8 weeks, what is established?
* What happens at this time?
* The primordia (an organ or tissue in its earliest recognizable stage of development) of each organ system is established
* At this time each organ is most sensitive to the induction of a birth defect
51
During the rest of gestation (week 9 to birth) other sensitivities may occur such as what?
* the brain continues to develop and remains sensitive to insult from many factors, including drugs like alcohol (alcohol exposure during gestation is the leading cause of mental retardation)
* However, the baby is less likely to have a major structural defect induced after the eighth week
52
* Where does fertilization occur?
* What happens as the embryo moves down the tube towards the uterus?
* What happens at day 5-6 days?
* **Fertilization** occurs in the ampullary region of the uterine **(Fallopian) tube**, and embryonic development begins immediately.
* Development continues as the embryo moves down the tube toward the uterus. **By 3 days, the morula (mulberry) stage is attained**; by **4-5 days, the blastocyst stage** is observed, and the embryo enters the uterine cavity.
* **At 5-6 days, the blastocyst implants.**
53
* Cells move in through all regions of the primitive streak, including the what?
* As they move through the streak, their fates are specified. What is an example?
* Cells move in through all regions of the primitive streak, including the node.
* As they move through the streak, their fates are specified. For example, cells moving through the most cranial aspect of the primitive node will form prechordal and notochordal cells; just lateral to this region, cells will form heart cell precursors and so on.
54
* Induction of the neural plate occurs how?
* While the neural plate is induced cranially, what happens?
* Once the neural plate is induced, it begins what?
* Induction of the neural plate occurs in a cranial-to-caudal sequence; thus, the head region is induced first.
* Note that while the neural plate is induced cranially, the **primitive streak and gastrulation continue caudally- its happening at the same time**
* Once the neural plate is induced, it begins to elevate above the remainder of the epiblast. **This initiates the process of neurulation.**
55
* What is neurulation?
* The neural plate continues to elevate and forms a fold on each side of the midline (neural folds). What does this create?
* Somites are formed from what?
* **Neurulation** is the process of creating the neural tube from the neural plate.
* The neural plate continues to elevate and forms a fold on each side of the midline (neural
folds). The groove created in the midline is called the neural groove.
* Somites are formed from mesoderm and play a major role in vertebrae formation.
56
At this 20-day stage, the process of gastrulation has made enough cells to form what? But not enough for what?
At this 20-day stage, the process of gastrulation has made enough cells to form most of the head and neck region, but cells for the thorax, abdomen, pelvis, etc., have not yet migrated through the primitive streak. Thus, if gastrulation stopped at this time, the head and neck would be the only structures formed.
57
* Neural crest cells form where?
* NCC are important why? Give an example?
**Neural crest cells** form in the edges (crests) of the neural folds as neurulation
proceeds
Neural crest cells are **extremely important** because they migrate to many places and form all kinds of tissues.
* *For example*, they form parts of the skull and all of the bones of the face, neural ganglia for the gut, melanocytes, and septa for the outflow tract of the heart. They are incredibly sensitive to insults from toxic factors (teratogens) and are involved in many birth defects.
* Thus, many **craniofacial and heart defects are due to abnormalities of neural crest cells.** In fact, many infants with craniofacial defects will also have heart malformations because of the involvement of these cells in both sites
58
* Neural crest cells leave the cranial neural folds prior to what?
* Where do these cell migrate?
* Neural crest cells leave the cranial neural folds prior to closure of the neural tube.
* These cells migrate into the facial region, which at this stage is represented by the pharyngeal arches. Later, each arch contributes specific structures to the head and neck region.
59
When does the neural tube closed and gastrulation complete?
28 Days
60
Even though the discussion has focused on formation of the neural tube, it is important to note that many other systems have been developing simultaneously. Which ones?
The eye (optic vesicle), ear (otic vesicle), mouth, heart, somites, and many other structures have also formed over this same time period (third and fourth weeks)
60
Spina bifida:
* Arises when?
* Can occur when?
* Defects results in what?
* The defect arises when neural tube closure fails in the spinal cord region.
* The defect can occur at any spinal cord level but is present most frequently in the lumbosacral area.
* The defect results in a loss of function depending on the level of the lesion (very similar to a
spinal cord injury). Most people with this defect have difficulty walking and may require braces or crutches or be confined to a wheel chair. They may also have problems with bowel and bladder functions.
61
Spina bifida:
* The defects are not what?
* Stillborn shows what?
* What happens in some cases?
* The defects are not lethal and do not affect intelligence. They can be repaired.
* The stillborn shows a typical lesion with neural tissue exposed (spina bifida cystica).
* In some cases, the neural tube may close, but vertebrae do not form around the tube.
* This type of defect is usually covered by skin, and the skin may have many dark, coarse hairs
(spina bifida occulta).
* Children with this defect do not have neurological impairments. However, they have the same
higher chance of having a child with an NTD as someone who has a more severe defect.
62
How can you prevent neural tube defects folic acid?
* Who remembers the issue with folic acid and absorption??
* PREVENTS 70% of NTDs
* Folic acid has been added to many cereals and grains but not in sufficient quantities: supplementation with a multivitamin is essential.
* Since50%ofall pregnancies are NOT planned, every woman of childbearing age should take a multivitamin with 400 μg folic acid every day
63
* During month one, there is how many body cavities?
* What is separated?
* The septum transversum is derived from what?
* There is only one continuous body cavity at this stage (4 weeks).
* However, the thoracic and peritoneal cavities are partially separated by a proliferation of
mesoderm called the **septum transversum.** (It will help form the diaphragm; the central tendon.)
* The septum transversum is derived from visceral mesoderm surrounding the heart, and it is
brought to its present location by the head fold
64
* What does body folding creates?
* At this early stage, the cavity is continuous from what?
* **Body folding creates the primitive body cavity lined by the visceral and parietal layers of lateral plate mesoderm. These layers differentiate into serous membranes lining all the body cavities.**
* At this early stage, the cavity is continuous from the head to tail of the embryo (i.e., it has not been subdivided into the peritoneal, pleural, and pericardial cavities)
65
# Week 5
* Proliferation and differentiation of some of this mesoderm forms what?
* What is an interesting point?
Again: Proliferation and differentiation of some of this mesoderm forms the **septum transversum,** and folding of the head region carries this tissue into the thoracic region.
* Folding brings things mid line
**Interesting point**: The heart begins development in front of the brain, explaining why some people “lead with their hearts.” It all has an embryonic origin!
66
# week 5
* Positioning of the septum transversum creates what?
* n addition to forming the central tendon of the diaphragm, the septum transversum forms what?
* At 7 weeks the esophagus passes where?
* Positioning of the septum transversum creates the two pericardioperitoneal canals posteriorly, which connect the primitive thoracic and peritoneal cavities for a short time.
* **In addition to forming the central tendon of the diaphragm, the septum transversum forms the connective tissue for the liver as hepatic cells grow into this region.**
* At 7 weeks the esophagus passes through the diaphragm (as does the inferior vena cava and the aorta)
67
THE FORELIMB DEVELOPS AHEAD OF what?
THE HINDLIMB BY ABOUT 24 HOURS. BY 8 WEEKS, THE LIMBS ARE WELL FORMED WITH FINGERS AND TOES
68
# VENTRAL WALL CLOSING
* the folds move ventrally, they pull what?
* At the point of fusion, what must take place?
* What closes as well and what is it suspended by?
* Note that as the folds move ventrally, they pull the amnion with them so that it eventually surrounds the embryo.
* At the point of fusion, are arrangement of tissues must take place so that fusion can occur properly between the different layers.
* The gut tube closes as well and becomes suspended from the dorsal body wall by a dorsal mesentery.
69
# VENTRAL WALL CLOSING
* Both the head and tail regions of the embryo lengthen and move ventrally, creating what?
* As the gut tube forms, what happens?
* Note that all the folding creates what?
* Both the head and tail regions of the embryo lengthen and move ventrally, creating the head (cranial) and tail (caudal) body folds.
* As the gut tube forms, a connection is maintained from the midgut to the yolk sac via the vitelline (yolk sac) duct. Normally, this attachment degenerates around the 14th week
* **Note that all the folding creates the fetal position and that it centers on the umbilical region where the vitelline duct and connecting stalk are located**
70
What are ventral body wall defects?
* Ectopia Cordis
* Gastroschisis
71
What is ectopia cordis?
* Ectopia cordis is a rare congenital condition in which some or all of a baby’s heart doesn’t have the typical coverage of the breastbone. The heart instead lies beneath a layer of skin and appears to be outside the chest.
* The newborn heart has little protection from injury when it is in this position, so it’s imperative to move it into proper place as soon as the infant is healthy and strong enough for surgery. The term “ectopia cordis” is Latin: “ectopia” means “outside” and “cordis” means “heart.”
72
What is gastroschisis?
* The defect is usually to the right of the umbilicus, but we do not know why.
* The defect is typically (90%) in infants from younger mothers 18-22 years old.
* The incidence of the defect is increasing, but we do not know why.
* Frequency of other defects in these children is relatively low (15%).
* Part of the exposed bowel usually becomes necrotic and has to be resected; the amount lost dictates outcome for the patient.
73
* Sutures of fibrous tissue form where?
* What do they allow?
* Spaces where two or more sutures intersect are called what?
* What is the soft spot?
* When does the anterior fontanelle closes?
* Sutures of fibrous tissue form between bones of the skull to allow for expansion as the brain grows.
* They also allow the bones to overlap each other (molding) as the baby’s head passes through the birth canal.
* Spaces where two or more sutures intersect are called fontanelles.
* The anterior one forms the “soft spot” on a baby's head.
* In most cases, the anterior fontanelle closes by 18 months, while the posterior one closes by 1-2 months. Some stay open into adulthood.
74
CRANIOS YNOSTOSIS:
* What is it?
* Occurs in how many births?
* Due to what?
PREMATURE CLOSURE OF ONE OR MORE CRANIAL SUTURES
* Occurs in 1:2500 births
* Present in over 100 genetic syndromes
* Many are due to mutations
75
CRANIOSYNOSTOSIS:
* What suture is scaphocephaly and brachycephaly?
* Scaphocephaly: Sagittal suture.
* Brachycephaly: Coronal sutures
76
What is responsible for the outgrowth of limb segments?
The apical ectodermal ridge (AER)
77
* Cell death in the AER creates what?
* Programmed cell death (apoptosis) in 4 areas of the AER creates what?
* Digits continue growing under the influence of what?
* Interdigital tissue is removed by what?
* **Cell death in the AER** creates 5 separate AER regions for finger growth; then cell death in the interdigital spaces separates the fingers
* Programmed cell death (apoptosis) in 4 areas of the AER creates 5 digits.
* Digits continue growing under the influence of the remaining parts of the AER that cover each one.
* Interdigital tissue is removed by programmed cell death to create 5 separate digits
78
What is syndactyly
79
Development of the heart begins with what?
formation of a horseshoe-shaped endothelial tube (the primitive heart tube)
80
* Lateral folding creates what?
* What does cephalocaudal folding positions what?
* What is the heart suspended within and by?
* Lateral folding creates the heart tube by bringing together two precursor regions
* Then cephalocaudal folding positions the heart tube in the future thorax position
* The heart tube is suspended within the pericardial cavity by a membrane
81
* Fusion of the two sides heart precursors, produces what?
* The heart tube sprouts what?
* The caudal pole forms what?
* Fusion produces a single tube with aortic and venous poles.
* The heart tube sprouts aortic arch vessels from the (aortic) outflow region
* The caudal pole forms the venous end of the heart.
82
From superior to inferior, the primitive heart tube is compromised of six regions:
* Aortic roots (arterial poles)
* Truncus arteriosus
* Bulbous cordis
* Ventricle
* Atrium
* Sinus venosus (venous poles)
83
* What is cardiac looping?
* Even though it is just a tube, it is beating, and the different regions have begun to differentiate into?
* Cardiac looping is the process where the heart tube folds on itself to create the typical heart shape and location, typically around day 23
* Even though it is just a tube, it is beating, and the different regions have begun to differentiate: **primitive atria, primitive ventricle (left), bulbus cordis (right ventricle), and outflow tract**
84
The sinus venosus is responsible for what? Where does it receive blood from?
is responsible for the inflow of blood to the primitive heart and empties into the primitive atrium
* It receives blood from the left and right sinus horns
85
Over time the venous return shifts where?
shifts to the right side of the heart (absorbed by the growing right atrium and forming part of vena cava) causing the left sinus horn to recede and form the coronary sinus (responsible for the drainage of the venous blood form the heart itself)
86
The early arterial system begins as what?
begins as a bilaterally symmetrical system of **arched vessels**, which then undergo extensive remodeling to create the major arteries that exit the heart
87
What do the aortic arches form?
88
Each one of the arches has a corresponding nerve during development.
* List out for the right and left recurrent laryneal nerve
* Right recurrent laryngeal nerve- initially hooks around the right 6th aortic arch, but as things develop it moves up to hook around the right subclavian atch
* Left recurrent laryngeal nerve hooks around the 6th aortic arch
since the distal part persists as the ductus arteriosum, the nerve remains in this position
* Lives under the aortic arch
89
How does the septum primum forms?
* **First, septum (septum primum) grows downward** toward the fusing endocardial cushions that split the atrium into two.
* Before this septum fuses with these cushions and to allow continued flow of blood across this region, an opening is created near the top of the septum by programmed cell death (apoptosis).
* The opening between the septum and AV cushions is called the ostium primum, which closes as the second opening (ostium secundum) is formed by apoptosis
90
How do you form the septum secundum?
* A second septum (septum secundum) also grows from the roof of the atrium toward the fusing AV cushions, and it overlaps septum primum.
* The presence of both the ostium secundum and foramen ovale allows a right to left shunt to be present in the developing heart
* The timing is carefully controlled – at least one hole is present in the septa to allow communication between left and right atria
* Allows blood to be shunted to the left side of the heart, bypassing the non functional lungs
91
* What is the foramen ovale?
* The valve of the foramen is formed by what?
* What happens at birth?
* The foramen ovale is the opening in the septum secundum.
* The valve of the foramen is formed by the septum primum.
* At birth, pressure rises in the left atrium due to increased blood flow from the lungs, while pressure on the right decreases with clamping of the umbilical cord and decreased blood flow from the placenta.
* **These changes in pressure close the foramen ovale**.
92
How do you form the AV valves?
* As the AV cushions separate the AV canal into mitral and tricuspid openings, all four cushions (anterior, posterior, and two lateral) become fibrous.
* Their attachments to the ventricular walls become cord-like, forming the **chordae tendineae** (fibrous cords of connective tissue that connect the papillary muscles to the tricuspid valve and the bicuspid valve in the heart. )
* Muscular attachment sites elongate and form the **papillary muscles.**
93
* What signaling do you need for cardiac valves formation?
* What happens in mutations?
* NOTCH signaling is recognized as an essential molecular regulator of valve development, valvulogenesis
* NOTCH1 mutations are the first genetic variant identified for congenital bicuspid aortic valve
94
* Endocardial cushions function as what?
* What happens at birth?
Endocardial cushions function as valve primordia which undergoes the remodeling process until birth when the cellularized endocardial cushions eventually become the mature heart valves with thin leaflets
95
* What does NCC participate in?
* What do they populate?
* The fact that crest cells participate in what?
* Neural crest cells participate in septation of the outflow tract and perhaps other regions as well.
* They populate the endocardial cushion tissue essential to forming the septa
* The fact that crest cells participate in heart septation and that they make all of the bones of the face and some of the skull explains why many children with craniofacial defects (e.g., cleft lip or palate, etc.) also have cardiac defects
96
Blood flow into the forming fetus follows this pathway:
97
Blood flow back to the forming fetus follows this pathway
98
At birth, the umbilical cord is clamped, stopping blood flow from the placenta.
* What happens in response?
* In response, the ductus venosus closes and later becomes fibrotic, forming the **ligamentum venosum in the liver.**
* Pressure rises in the left atrium compared to the right due to increased blood flow from the lungs and decreased blood flow to the right side from the placenta.
* The pressure change **closes the flap over the foramen ovale**. Later, this flap will become fibrotic and permanently seal the opening.
99
What does bradykinin do?
* **Bradykinin** is secreted by the lungs and causes the **ductus arteriosus to close.**
* The ductus becomes fibrotic to form the **ligamentum arteriosum.**
100
During the first months after birth, babies may turn blue when they cry. Why is that?
This is because of pressure changes in the atria that open the foramen ovale and create a right (venous blood) to left (arterial blood) shunt. It requires some months for the atrial septa to fuse permanently.
101
What are the congenital heart defects?
102
BICUSPID AORTIC VALVE:
* At risk for what?
* Structurally gives what?
* At risk for developing calcified aortic valve disease decades earlier than those with a tri-leaflet valve
* Structurally gives abnormal blood flow dynamics and predisposes the valve to endothelial dysfunction and inflammatory activation
103
* The respiratory diverticulum lengthens to form what?
* What do the lung buds divide into?
* Form the trachea and then divides to form two lung buds
* These buds divide into three branches on the right and two on the left, reflecting the number of lobes of the respective lungs on those sides
104
The lung buds grow into what? What is it covered by?
The lung buds grow into the primitive pleural cavities and are covered by the visceral layer of lateral plate mesoderm (visceral pleura).
105
* The lung cavity is lined by what?
* The visceral and parietal layers are what?
* The cavity is lined by the parietal layer of lateral plate mesoderm that forms the parietal pleura.
* The visceral and parietal layers are continuous at the root (hilum) of each lung.
106
* What is type one and two alveolar cells?
* What happens with decreased surfactant?
* Type I alveolar cells = gas exchange
* Type II alveolar cells (6.5-7 months) = secrete surfactant = reduces surface tension in the alveoli so they can remain open during breathing. If not for surfactant, alveoli would collapse.
* 16% of alveolar cells are present at birth; remainder develop for 10 years
* Premature infants (<7 months) = respiratory distress syndrome (RDS) = insufficient surfactant = increased surface tension = collapse of alveoli
