Basic Embryology Flashcards
What are the 3 stages of development? What happens in each?
Cleavage - mitotic divisions of the zyote
Embryonic period - germ layers, main body systems and placenta, up to 2 months
Foetal period - further organ development and locomotor system becomes functional
Cleavage is the mitotic division of the zygote (fertilised ovum) into what structure?
Morula - sphere of cells
What stimulates morula cell division? What does this form?
Uterine secretion
Blastocyst
Cells are reorganised around the blastocyst cavity. The inner cell mass eventually becomes what? Which pole is this at?
Foetus - at animal pole
Opposite the vegetal pole
What is the trophoblast? What does it eventually become?
Outer superficial layer that develops through rearrangement of blastocyst cells
Foetal part of the placenta
What is implantation? Which way does the inner cell mass face?
Blastocyst loosely attaches to endometrium
Towards endometrium
The trophoblast develops into 2 layers, which go on to form what?
Foetal part of placenta
Chorion. (one of the membranes)
One of the trophoblast layers produces enzymes, what do these enzymes do?
Break down the endometrial cells, so the blastocysts can penetrate the uterus wall further
The inner cell mass eventually becomes the foetus. However, it differentiates first into the bilaminar disc, which is made up of what layers? What do these layers eventually become?
Hypoblast - goes on to form endoderm
Epiblast - goes on to form ectoderm
A cavity in the epiblast forms what? What do the epiblast cells become?
The amniotic cavity
Amnion - thin, protective foetal membrane
What happens to the amnion? What does it fill with? WHat is this?
Surrounds the embryo
Amniotic fluid - filtrate of mothers blood, contains foetal urine excretions
Hypoblast cells cover the inner surface of the blastocyst. These cells become what to form the exocoelomic membrane? What does the exocoelomic membrane and hypoblast form?
Squamous
Yolk sac
What is gastrolation? What does this establish?
the rearrangement and migration of the epiblast cells in the bilaminar disc
Body plan of the embryo
The bilaminar disc is transformed into the trilaminar disc. What are the epiblast cells now referred to as? What are the hypoblast cells referred to as? What becomes the mesoderm?
Ectoderm
Endoderma
Mesenchyme - loosely organise connective tissue
During gastrulation, which essential part of the body is formed?
CNS
Which tissues originated from ectoderm?
Nervous tissue Epidermis Lens/cornea Inner and outer ear Epi lining of oral and nasal cavities Renal medulla
What tissues originate from mesoderm?
All skeletal and cardiac muscle, most smooth muscle Cartilage, bone and connective tissue Epi linings of the visceral cavities Dermis Eyeball layers Adrenal cortex
Which tissues originate from endoderm?
Epi linings of the GI, urinary, genital and respiratory tract
Epi lining of the thyroid gland, pancreas and thymus
What is organogenesis? WHat are the parts to the gut?
Development of organ systems
Foregut, midgut, hindgut
What are pharyngeal clefts?
Grooves which seperate pharyngeal arches
What do the pharyngeal pouches develop with? What is the difference?
Pharyngeal arches and clefts
Pouches develop outside of the embryo
What is the allantois? What does it do for the embryo?
Sac with clear fluid and blood vessels
Nutrition and excretion for embryo
What are the 4 extraembryonic membranes?
Chorion
Allantois
Yolk sac
Amnion
