Finals Prep- Notes Flashcards
Primitive Streak
Midline thickening beginning at one end of the pellucida. Begins at the rear of the embryo. Caused by cells of the area pellucida migrating and converging on a midline. Extends about 3/4 of the way up the area pellucida, but never all the way. The rate of the cells leaving the primitive streak becomes greater than those forming causing the streak to recede in anterior to posterior direction.
In birds, it doesn’t completely recede, some remains and forms the tail.
Primitive knot
Slightly rounded enlargement at cranial end of the primitive streak.
Primitive Groove
Depression in the primitive streak and knot. Cells “dive” through. First cells form the endoderm, joining the hypoblast. Mesoderm is the second. The ones that do not drop through forms the ectoderm.
Immigration
Type of cell movement that causes the primitive streak/groove/knot and the following germ layers.
Organogenesis
As soon as germ layers form, organs immediately begin to form, even if gastrulation isn’t 100% complete.
Neural Plate
Ectodermal
a cell mass falls out of the ectoderm and moves into the interior of the embryo, above the mesodermal layer. Folds into a cylinder
Neural tube
Cylindrical neural plate. Nervous system beginning. Ectoderm seals the gap.
Neurulation
Process of closing the neural plate into the neural tube
Notochord
Mesodermal. Forms in the center of three mesodermal masses.
Will be completely eliminated by the end of development. Early sensory rod for the fetus, but is gradually replaced by bone.
Mesodermal segments
Two remaining mesodermal derivatives. On either side of the notochord.
In humans, they are called “somites”
Break into three populations of cells (each segment):
- Dermatome, migrates and layers under epidermis to form dermis
- Sclerotome: Forms the skeleton
- Myotome: Muscle (all three types: cardiac, skeletal, and smooth).
Cerebral Hemispheres
Telencephalon. Ectoderm
Consists of both white and grey matter. White is core, surrounded by grey. Most sophisticated functions come from the grey matter. Grey matter is often called the “cerebral cortex”.
Cerebellum
Ectodermal
Sits inferior and posterior to the brain. Balances and regulates skeletal muscle movement.
Diencephalon
Ectodermal
Consists of:
- Epithalamus: cerebrospinal fluid produced here.
- Thalamus: the largest portion of diencephalon. It’s the relay center that addresses each impulse and sensory input. Sorting center.
- Hypothalamus: Major hormone producer, human emotions, massively important to diencephalon.
- Penal Gland: less than 1% of the human brain, hormone production (melatonin).
- Pituitary: “Master gland”.
Olfactory Lobes
Ectoderm
Sense of smell, directly under the frontal part of the hemisphere
Optic Vesicles
Ectoderm
Eyes
PNS
Ectoderm
Peripheral Nervous System:
The nerves that enter and exit the brain and spinal cord. 12 pairs of cranial nerves and 31 pairs of spinal nerves.
Lens
Ectodermal
Focusing crystal in eyes
Cornea
Ectodermal
Right in front, the tissue the covers the eyes. Involved in focusing.
Organs that develop from Mesoderm
Dermis, muscle, skeleton, blood vessels, ureters (drain urine from kidneys to bladder), bladder, urethra, gonads.
All blood vessel components are mesodermal derivatives:
- Arteries
- Arterials
- Capillaries
- Venules
- Veins
Endodermal Derivatives
GI Tract (mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus)
Pancreas, gallbladder, liver, kidneys, ducts that drain liver, gallbladder, and pancreas, eustachian tubes, thyroid, parathyproid, thymus
Liver
Makes bile (digestive fluid but not a digestive enzyme)
Ducts drain the bile from liver and into the right and left hepatic ducts (endodermal organs)
Continuously drips bile
Bile Ducts
Common hepatic duct
Cystic Duct: drains the gallbladder, connects to the hepatic duct.
Common Bile Duct: passes under the duodenum and emerges on the other side.