Richardson Flashcards
Organs from the Ectoderm
Nervous System
Epidermis (Hair and Glands)
Cornea and Lens
Morphogenesis
the movement of cells to form tissues
Organs from Mesoderm
Muscles Bones Cartilage Dermis Heart Blood Vessels Blood Cells Kidneys Gonads Reproductive Tracts
Organs from Endoderm
GI Tract Epithelium Liver
Pancreas Pharynx
Thyroid Parathyroid
Respiratory Tract Epithelium Bladder
Gastrulation
Establishment of the three embryonic germ layers
Basic Embryo Timeline
Weeks 1-3: Fertilization through Gastrulation (Primary Germ Layers)
Weeks 3-8: Embryonic Period (Organogenesis)
Weeks 9-38: Fetal Period (Maturation of Tissues and Organs)
Week 1 Embryo Timeline (day by day)
1: Fertilization (Zygote)
2: 2 Cell
3: Morula
4: Early Blastocyte
5: Late Blastocyte
6: Beginning of Implantation
7: Invasion of Endometrium
Where does fertilization take place?
In the Ampulla of the oviduct (Fallopian tubes)
Compaction
cells begin to clump and become increasingly less distinct (during the eight cell stage)
Blastoceol
a cavity formed by the accumulation of fluid between cells (very early blastocyst phase)
Hatching of Blastocyst
the breaking of the blastocyst out of the zona pelucida (necessary for implantation to occur)
What two layers does the inner cell mass divide into?
Epiblast: forms all tissues of the embryo
Hypoblast: forms extraembryonic tissue
When does the primitive streak begin to appear?
The end of week two/beginning of week 3
Primitive Node
Anterior end of the primitive streak (also known as Henson’s node)
Which cells are responsible for forming the notochord?
Mesodermal Cells
What is the only structure formed directly from the notochord?
Nucleus Pulposus
Prechordal Plate
region between the oropharangeal plate and the notochord; contributes to structures in the forebrain and oral cavity
Cloacal Membrane
Site of future anus; Allantois forms as a diverticulum from the yolk sac which then forms part of the cloaca
Sacrococcygeal Teratoma
Remnant of the primitive streak (when it doesn’t regress all the way); mostly in females; generally benign tumors containing tissues from all three germ layers
Neural Tube Defects: Two Types
Anencephaly: failure to close neurotube at the cranial end
Spina Bifida: failure to close neurotube from the cervical region to the caudal end
Can be prevented by folic acid intake before and during pregnancy
What structures derive from Neural Crest Cells?
Variety of Structures in the head
Ganglia
Adrenal Medulla
Melanocytes
Mesoderm Layers from Most Cranial to Most Caudal
Paraxial
Intermediate
Lateral Plate (Splits into Parietal/Somatic and Splanchnic/Visceral)
Extraembryonic
Paraxial Mesoderm
Organizes into paired somites adjacent to neural tube and notochord; forms axial skeleton, associated muscle, and dermis; number of somites can be used to date the embryo
Cells from Somites form:
Dermatome (Dermis)
Myotome (Muscles)
Sclerotome (Tendon, Cartilage, Bone)
Intermediate Mesoderm
Forms urogenital structures (parts of urinary system and gonads)
Coelem
Body Cavity; formed by the lateral folding of the embryonic disk (closes wall of gut in the process)
Somatic/Parietal Lateral Plate Mesoderm
forms the body wall
Visceral/Splanchnic Lateral Plate Mesoderm
covers organs
Hemangioblasts
formed from mesoderm layers; common precursors to blood cells and vessels
Angiogenesis
sprouting of blood vessels from existing ones
Vasculogenesis
Blood island appears in wall of yolk sac beginning week 3
Liver major site of hematopoeisis from 2-7 months
After 7 months, stem cells in bone marrow take over
Three types of cartilage and their locations/functions
Hyaline: developing skeleton of embryo, epiphyseal plate of growing bones, articular cartilage, respiratory tract
Elastic: ear, epiglottis, and eustachian tube
Fibro: Intervertebral Disks, meniscus of the knee, Mandible, sternoclavicular joints, pubis symphosis
Hyaline Cartilage
Most common
Type 2 Collagen, Proteoglycans, and Water
Perichondrium (except for articular cartilage)
Glassy appearance
Resists Compression
Appositional Growth
Cells from inner layer of perichondrium differentiate into chondroblasts; deposit matrix next to existing matrix
Interstitial Growth
Growth of chondroblasts by mitosis within the cartilage matrix; new territorial matrix deposited; forms isogenic groups
Elastic Cartilage
Matrix is Type 2 Collagen
Elastic Fibers
Perichondrium
Fibrocartilage
Type 2 and Type 1 Cartilage in dense regular pattern
Resists compression and stretching
No perichondrium
Osteoblasts
Originate from osteoprogenitor cells
Cuboidal or columnar epithelial like cells
Secrete osteoid and form new bone
Osteoclasts
Derived from monocyte/macrophage lineage
Break down bone through acidic environment (H+ ATPase)
Reside in Howship’s Lacuna
Bone Matrix Composition
Osteoid: Type 1 Collagen fibers, proteoglycans, noncollagenous proteins
Inorganic: Calcium phosphate
Interstitial Lamelae
partial osteons in the middle of compact bone; left over from remodeling
Ground Bone
structures are visible but cellular components are destroyed
Decalcified Bone
Cells are left in tact but structure is hard to see
Intramembranous Osteogenesis
Forms directly in mesenchyme; used to form skull bones
Endochondral Osteogenesis
forms in a cartilage template; process used to form long bones
