Embryo development Flashcards
what are the six features common to all chordates?
Notochord pharyngeal slits Endostyle or thyroid gland postanal tail Segmented body musculature
What are some features of the notochord?
Slender, fibrous, longitudinal rod Embryologically derived from mesoderm Dorsal to the coelom Ventral to the central nervous system Provides stiffness for the animal Bends laterally, resists cranio-caudal compression Primitive function replaced by vertebral column
What are some functions of the pharyngeal slits?
Walls of the pharynx are pierced or almost pierced (pharyngeal pouches) In fish, gills form next to pharyngeal slits Hence the incorrect term “gill slits” Probably functioned in feeding and/or respiration in early chordates
What is an endostyle?
a ciliated groove in the floor of the mouth in early chordates
thyroid gland
present in more advanced chordates
What are some feature of the dorsal hollow nerve tube?
Central nervous system in chordates is develops embryologically from ectoderm During neurulation, ectoderm rolls up, leaving a hollow core Your spinal cord has a small canal down the center (neurocoel)
What are some features of the post anal tail?
a tail extending beyond the lower anus primarily used for swimming in early chordates. only present in humans in embryonic stage. develops into the coccyx
What are some features of segmented body musculature?
blocks of muscle arranged along the length of the body.
Where is segmentation mostly found in humans?
found in mesoderm derivatives = somites->dermatome, myotome, sclerotome
What is gastrulation?
Formation of the three germ layers, Ectoderm, mesoderm, and endoderm
- epiblast cells begin to migrate ventrally toward primitive streak
- they move ventrally toward hypoblast. the intermediate layer becomes the mesoderm
- this invagination progresses caudal to cranial
What becomes the epidermal Ectoderm?
Epidermis - skin, hair follicles & hair, nails
Anterior mouth
Terminal GI system
What becomes the Neural plate Ectoderm?
Central Nervous system (brain and spinal cord)
What becomes the Neural crest ectoderm?
Peripheral nervous system - nerves outside CNS
Ganglia of nervous system (cranial, spinal, autonomic)
Dentine of teeth
Head skeleton
Pigment cells
Covering of the brain (meninges)
What are the divisions of the mesoderm?
Epimere
mesomere
hypomere
What does the epimere form?
dermatome - dermis of skin
Myotome -Axial, limb, and body musculature
Sclerotome - vertebral column and ribs
What is a blastula?
is a hollow sphere of cells, referred to as blastomeres, surrounding an inner fluid-filled cavity called the blastocoele formed during an early stage of embryonic development in animals
What is athe Dorsal hollow nerve cord and where is it located?
The dorsal nerve cord is one of the embryonic features unique to chordates, along with a notochord, a post-anal tail, an endostyle, and pharyngeal slits. The dorsal nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube, compared to other animal phyla, which have solid, ventral tubes. The dorsal nerve cord is later modified in vertebrates into the central nervous system which is composed of the brain and spinal cord. Dorsal nerve cord is mainly found in subphylum Vertebrata.
