Chapter 15- Lateral mesoderm and endoderm Fig. 14.1- mesoderm lineages Recall lineages Fig. 12.4 Paraxial Head Somite Cartilage, skeletal, dermis Intermediate Kidney, gonads Notochord Lateral Circulatory, Body cavity, extraembryonic 3 regions: Fig. 14.1- mesoderm lineages a. _________________ -becomes body cavity wall b. _______ -becomes the body cavity c. ___________________ -becomes body cavity wall and the the heart

How does the heart develop?? c. Splanchnic mesoderm Lateral mesoderm How does the heart develop?? 25hr 26hr Fig. 15.3 ___________ 1. Splanchnic mesoderm halves begin to ______ 2. These cells differentiate into ___________ (heart lining and valve precursors and ______________ (heart muscles) 72hr 28hr 27hr Myocardium 3. Endocardium tubes _______ 4. Mycocardium ________ 5. Heart begins beating even while ________ is occurring

Fig. 15.13- “extra” archs in mammal development Blood vessel formation Lateral mesoderm 2 steps- 1._____________ and 2. ____________ Note: Blood vessels form independently of the heart, then link up Some background Info Constraints on blood vessel construction ____________ an organism must: Obtain ___________before the intestine develops Use __________ before there are lungs Excrete _________ before there are kidneys Fig. 15.13- “extra” archs in mammal development 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

Blood vessels and blood cells are intimately connected Blood vessel formation Lateral mesoderm 1. Vasculogenesis Fig. 15.14 Blood vessels and blood cells are intimately connected BMP Endothelial cells line __________ Angiogenic cell cluster (_________________) Fig. 15.16 Primitive blood cells __________ __________cells

Transcription factors in vasculogenesis Lateral mesoderm 1. Vasculogenesis Transcription factors in vasculogenesis 1. _______ is required for _____________formation 2. ________ is required for blood island and blood vessel formation VEGF is a target for ______________ “Tumors gotta eat” 3. ______ is required proper blood vessel formation (involved in communication between endothelial cell and _____________)

________ stabilizes capillary network 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 _______! ________ stabilizes capillary network VEGF plays key role ______ recruits pericyte cells to ensure __________ of capillaries

Arterial (__________) Venous (______) Lateral mesoderm 2. Angiogenesis Arteries vs. veins?? Arteries have _____________in cell membranes Veins have _________________ (called EphB4) in cell membranes Arterial (__________) Venous (______) Fig. 15.17 Functions of the EphrinB2/EphB4 system Ensure that arteries only link up with _____, not other arteries Ensure capillary fusion only occurs with like cells (e.g. only arteries with arteries)

Many organs make their own angiogenesis factors 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 ___________

Development of Blood Cells Fig. 15.20 Lateral mesoderm Development of Blood Cells Fig. 15.20 ____________ – embryonic cells capable of producing many cell types, including other ______________ Largest population of stem cells is in the _______________ “Committed” “Differentiating” “Differentiated” Stem Cell (CFU-M,L) B-cell lineage T-cell lineage

Myeloid precursor cell Lateral mesoderm Development of Blood Cells The stem cell (CFU-M,L) also gives rise to another cell lineage: “Committed” “Differentiating” “Differentiated” Stem Cell (CFU-M,L) B-cell lineage ____________ Platelets _________ T-cell lineage Myeloid precursor cell Eosinophils ___________ Fig. 15.21 ____________ ___________ factors that direct blood cell formation are termed “_________” Note that this is the point of ___ _______- cells are __________ to a becoming only one cell type

Angiogenic cell cluster Lateral mesoderm Development of Blood Cells Blood development (hematopoiesis) occurs in two phases: 1. _____________ Angiogenic cell cluster (blood islands) Occurs in blood islands in mesoderm near the yolk (recall fig. 15.16) Supplies developing embryo with oxygen ___________ inhibit blood and blood vessel formation Fig. 15.16 __________- disappear later in development Example- In mouse, stem cells originate in yolk sac, then later in AGM region 2. ___________ Formed in nodes of mesoderm surrounding aorta (in a region called the _________________________ (AGM) region) Lasts the _______ of the individual Fig. 15.24

(Esophagus,stomach,small intestine,colon) Endoderm Recall Fig. 12.4 Embryonic endoderm gives rise two ____ Endoderm Buds into __________ tube (Esophagus,stomach,small intestine,colon) _____, _________, pancreas Primitive gut endoderm __________ tube _________ 1. _______ endoderm – tissues are derived from _________________ Auditory cavities Tonsil walls _______(T-cell development) ______________ Pharyngeal arches Fig. 13.1 _____(sprout form base of forth arch)

2. ____________ endoderm Liver bud Stomach The _________________ buds out form the foregut, then branches to form ________, _________ and ___________ Gall Bladder Pancreas (ventral) Pancreas (dorsal) The ____________ is actually formed by the fusion of two distinct buds (one ventral and one dorsal) Fig. 15.29

What directs formation of liver from the endoderm?? The notochord (and mesenchyme) produces factors that ________ liver induction The __________________ secretes ____ that ________ the factors that inhibit liver induction Thus, _____signals the __________ region of the endoderm to become liver Fig. 15.30

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 foregut Pharynx trachea Lung buds esophagus Fig. 15.31 Week 4 (humans)

Problem Solution Four problems of a land-dwelling egg Day 2 chick embryo Problem Solution 1. ____________ Amnion secretes amnionic fluid into ________ 2. ____________ ______ exchanges gases 3. ____________ _________ supplies nutrients from blood vessels in yolk Day 9 chick embryo 4. ____________- ________ holds waste (vestigal in humans) Fig. 15.33