1)List the histological germ layers and describe organs originating from each layer.
2)Describe the differences between recessive, dominant, and co dominant genetic traits.
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I. Histological (Embryonic) Germ Layers
Three embryonic germ cells are the source of all cells of the human body, the ectoderm, mesoderm, and endoderm (Gest, 2000; National Institute of Health [NIH], 2009; Seeley, Stephens & Tata, 2004).
The ectoderm refers to the outer layer of the trilaminar embryonic disc (Gest, 2000; NIH, 2009). It is responsible of forming the following structures:
?Lens of eye
?Anterior pituitary gland
?Components of the vestibulocochlear nerve (CN VIII) - utricle, semicircular ducts, and vestibular ganglion
?Epithelial lining of external ear
?Olfatory nerve (CN I), olfactory placode
?Epithelial lining of anterior two thirds of tongue, the hard palate, sides of the mouth, teeth, and parotid glands and ducts
?Epithelial lining of lower anal canal
?Epithelial lining of distal penile urethra
?Epidermis, hair, nails, sweat and cutaneous sebaceous glands (Gest, 2000; NIH, 2009)
A portion of the ectoderm, called neuroectoderm develops all neurons within the central nervous system, all glial (supporting) cells within the central nervous system, retina, pineal gland and posterior pituitary gland(Gest, 2000; Seeley, Stephens & Tata, 2004).
There are groups of cells that break away from the neuroectoderm during development, called neural crest cells (Seeley, Stephens & Tata, 2004). They are the source of most of the peripheral nervous system, bones in the face and neck area and some muscles(Gest, 2000; NIH, 2009; Seeley, Stephens & Tata, 2004). Specifically, they originate the:
?Postganglionic sympathetic neurons ...
The solution includes two answers.
The first answer is a detailed list of the organs and structures originating from the three embryonic germ layers: ectoderm, mesoderm, and endoderm.
The second answer gives the explanation of the different patterns of inheritance: recessive, dominant, and codominant. References are given.