Chapter 15- Lateral mesoderm and endoderm

Recall lineages

Fig. 12.4

Fig. 14.1- mesoderm lineages

Intermediate

Kidney, gonads

Paraxial

Head Somite

Cartilage,skeletal, dermis

Lateral

Circulatory,Body cavity,

extraembryonic

Notochord

Fig. 14.1- mesoderm lineages

a. _________________

c. ___________________

b. _______ -becomes the body cavity

-becomes body cavity wall and the the heart

-becomes body cavity wall

3 regions:

How does the heart develop??

1. Splanchnic mesoderm halves begin to ______

2. These cells differentiate into ___________ (heart lining and valve precursorsand ______________ (heart muscles)

25hr 26hr

___________

3. Endocardium tubes _______4. Mycocardium ________

Fig. 15.3

27hr 28hr

5. Heart begins beating even while ________ is occurring

72hr

Myocardium

Lateral mesodermc. Splanchnic mesoderm

Blood vessel formation

Note: Blood vessels form independently of the heart, then link up

Constraints on blood vessel construction1. ____________ an organism must:

• Obtain ___________before the intestine develops• Use __________ before there are lungs• Excrete _________ before there are kidneys

2. ________________-• Six pairs of __________ loop

out- these enable primitive fish gills to oxygenate blood, but these serve no obvious purpose in mammals and birds.

3. ____________- Blood flows easier through large vessels, yet efficient ____________requires small vessels and ________________ blood

Solution- Large vessels branch into very small ones with overall more cumulative volume capacity

Fig. 15.13- “extra” archs in

mammal development

2 steps- 1._____________ and 2. ____________

Some background Info

Lateral mesoderm

1. Vasculogenesis

Blood vessels and blood cells are intimately

connected

Endothelial cells line __________

Fig. 15.14

Angiogenic cell cluster(_________________)

__________cells__________

Primitive blood cells

Fig. 15.16

Blood vessel formation

BMP

Lateral mesoderm

Transcription factors in vasculogenesis

1. _______ is required for _____________formation

2. ________ is required for blood island and blood vessel formation

3. ______ is required proper blood vessel formation (involved in communication between endothelial cell and _____________)

1. Vasculogenesis

VEGF is a target for ______________

“Tumors gotta eat”

Lateral mesoderm

2. Angiogenesis

Definition- _________ and _______ of capillary beds, arteries and veins

Note- Capillary networks of each organ arise within the organ itself, not from larger _______!

VEGF plays key role

________stabilizes capillary network

______ recruits pericyte cells to ensure __________ of capillaries

Lateral mesoderm

2. AngiogenesisArteries vs. veins??

•Arteries have _____________in cell membranes

•Veins have _________________ (called EphB4) in cell membranes

Functions of the EphrinB2/EphB4 system1. Ensure that arteries only link up with _____, not other arteries2. Ensure capillary fusion only occurs with like cells (e.g. only

arteries with arteries)

Arterial(__________)

Venous(______) Fig. 15.17

Lateral mesoderm

2. Angiogenesis

Many organs make their own angiogenesis factors

•Example- placenta

Developing placenta secretes ___________ to promote angiogenesis, then later secretes ___________________ to inhibit angiogenesis

Angiogenesis plays key role in tumor development

•A tumor must induce _________________ in order to ______

•Hence, if use a drug that inhibits this ______________, can possibly slow cure some ___________

Lateral mesoderm

Development of Blood Cells

____________ – embryonic cells capable of producing many cell types, including other ______________

Largest population of stem cells is in the _______________

Fig. 15.20

Stem Cell (CFU-M,L)

“Committed” “Differentiating” “Differentiated”

B-cell lineage

T-cell lineage

Lateral mesoderm

Development of Blood Cells

Fig. 15.21

Stem Cell (CFU-M,L)

“Committed” “Differentiating” “Differentiated”B-cell lineage

T-cell lineage

The stem cell (CFU-M,L) also gives rise to another cell lineage:

Myeloid precursor cell

____________

Platelets

_________

Eosinophils

___________

____________

Note that this is the point of ___ _______- cells are __________ to a becoming only one cell type

___________ factors that direct blood cell formation are termed “_________”

Lateral mesoderm

Development of Blood Cells

Blood development (hematopoiesis) occurs in two phases:

1. _____________

• Occurs in blood islands in mesoderm near the yolk (recall fig. 15.16)

Angiogenic cell cluster

(blood islands)

Fig. 15.16

• Supplies developing embryo with oxygen• ___________ inhibit blood and

blood vessel formation• __________- disappear later in development

2. ___________

•Formed in nodes of mesoderm surrounding aorta (in a region called the _________________________ (AGM) region)•Lasts the _______ of the individual

Example- In mouse, stem cells originate in yolk sac, then later in AGM region

Fig. 15.24

Lateral mesoderm

Endoderm

EndodermEmbryonic endoderm gives rise two ____

__________ tube(Esophagus,stomach,small intestine,colon)

__________ tube

Buds into _____, _________, pancreas

_________

Primitive gutendoderm

Fig. 13.1Pharyngeal

arches

Auditory cavities

Tonsil walls

_______(T-cell development)

___________________(sprout form base of forth arch)

Recall Fig. 12.4

1. _______ endoderm – tissues are derived from _________________

2. ____________ endoderm

The _________________ buds out form the foregut, then branches to form ________, _________ and ___________

StomachLiver bud

Gall Bladder

Pancreas(ventral)The ____________ is actually

formed by the fusion of two distinct buds (one ventral and one dorsal)

Pancreas(dorsal)

Fig. 15.29

Fig. 15.30

The __________________ secretes ____ that ________ the factors that inhibitliver induction

The notochord (and mesenchyme) produces factors that ________ liver induction

What directs formation of liver from the endoderm??

Thus, _____signals the __________ region of the endoderm to become liver

The respiratory tube

• ______ are one of the last _________ to differentiate

• Alveolar cells of the lung produce _________ at 34 weeks gestation

• Thus, a premature infant cannot breathe properly

Fig. 15.31

foregut

Lung buds

Pharynx

trachea

esophagus

Week 4 (humans)

Four problems of a land-dwelling egg

1. ____________

SolutionProblem

Amnion secretes amnionic fluid into ________

2. ____________

4. ____________-

3. ____________

______ exchanges gases

________ holds waste (vestigal in humans)

_________ supplies nutrients from blood vessels in yolk

Day 2 chick embryo

Day 9 chick embryo

Fig. 15.33