1. Bio 255 SI
Tyler Forero

2. Icebreaker Questions
Have you taken the exam yet? If so, how did it go?
When do you plan on taking your second attempt?
What topics are you struggling with most in unit 1?

3. Review from Last Week Development: Egg to embryo
Terms to refer to human offspring prior to birth
Meiosis
Fertilization
What makes it so that only 1 sperm cell can enter an egg?
Embryoblast vs trophoblast
Gastrulation – epiblast cells enter through primitive streak forming endoderm and mesoderm. 3 germ layers are formed after gastrulation.
Fertilization zygote blastocyst  embryo  fetus  birth = baby
Meiosis has synapsis and crossing over during prophase 1 that leads to diversity. Results in 4 distinct daughter cells
Fertilization occurs in uterine tubes
Blastocyst will bind to uterine wall. Embryoblast is inner portion that becomes 3 germ layers. Trophoblast is outer that becomes placenta
Zona reaction (cortical) hardens the outside of the egg so nothing can enter.

4. Gastrulation + Neurulation

5. What did we learn about Thursday?
Embryonic Membranes
Integumentary system functions
Layers of skin
Hair, nails, glands
Review: What does the endoderm, ectoderm, and mesoderm eventually become? (derivatives of...)
endoderm: mucousal membranes, ex: lining of respiratory/digestive tract, glands
mesoderm: blood, serous membranes, connective tissue, organs, bones
ectoderm: skin, nervous tissue, pituitary gland

6. Label the layers of the epidermis.
Living keratinocyte
Langerhaan (dendritic) cells
Tactile cell
Basement membrane
Sensory nerve ending
Dead keratinocyte
melanocyte
Stratum Corneum
Stratum Lucidium
Dermis
Stratum Spinosum
Stratum Basale
Stratum Granulosum

8. Label

9. Integument

10. What are the functions of the skin?
Barrier – protection
Body temp regulation
Cutaneous sensation
Metabolic functions – synthesis of vitamin D
Blood reservoir

11. What is the function of the following embryonic membranes?
Amnion: epiblast cells form transparent membrane filled with amniotic fluid
Buoyant environment protecting embryo
Helps maintain homeostatic temp
Amniotic fluid comes from maternal blood, and later, fetal urine.
Yolk sac: hypoblast cells form sac on the ventral surface of embryo
Forms part of digestive tube
Produces earliest blood cells and vessels
Source of primordial germ cells –
Chorion – outermost membrane and is formed by syncytiotrophoblast and cytotrophoblast cells.
Function – formation of the embryonic part of the placenta
Develops fingerlike villi for nutrient exchange

12. Review
1. The muscle that is made of striated, branched, uni or bi-nucleate cells under involuntary control: _______________
2. The muscle that is made of striated, multi-nucleate cells under voluntary control: _______________
3. The muscle that is made of short, fusiform, uni-nucleate cells under involuntary control: _______________
4. Which comes first gastrulation or neurulation?
5. What does the endoderm, ectoderm, and mesoderm eventually become? (derivatives of...)
Cardiac muscle
Skeletal muscle
Smooth muscle
Gastrulation.
endoderm: mucousal membranes, ex: lining of respiratory/digestive tract, glands
mesoderm: blood, serous membranes, connective tissue, organs, bones
ectoderm: skin, nervous tissue, pituitary gland