Bio 255 SI Tyler Forero

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?

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.

Gastrulation + Neurulation

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

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

Label

Integument

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

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

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