Lecture 1 Flashcards
When does the embryonic period start and end?
Starts as soon as the egg becomes fertilized, it becomes an embryo and stays such for 9 weeks.
During week 3, the embryionic cells flatten into a _____
trilaminar disc
What are the layers in the trilaminar disc?
Endoderm, Mesoderm and Ectoderm
What does the Endoderm develop into?
Inner lining of the digestive and respiratory tracts, glands (including liver and pancreas)
What does the Mesoderm develop into?
Muscle, bones, cartilage, circulatory system, dermis, CT
What does the Ectoderm develop into?
Brain and nervous system, epidermis (skin, hair, nails, etc.)
What happens during the 4th week of the Embryonic period?
The paraxial mesoderm thickens and divides into paired masses on either side of the notocord, called somites. This is the beginning of the segmentation of the spinal cord.
What does the dermatome further separate into?
the dermis/skin
What does the myotome further separate into?
the muscles of the back, thorax, and limbs
What does the sclerotome further separate into?
the vertebrae and ribs
During which week do limb buds develop, and from which layer(s)?
Week 5 the limb buds appear from the ventrolateral walls of the embryo. Limb buds consist of mesoderm (lateral somite) and ectoderm (apical ectodermal ridge)
Which type of cells develop into the muscle and cartilage of the limb buds?
Myotome
How do spinal nerves migrate?
They migrate with the myotome cells to innervate the muscles
What week do cartilage models of the bones and arm begin to form?
Week 6.
At what week does Enchondral ossification begin?
Week 7
Mesenchymal cells condense into precartilaginous aggregates and differentiate into _______ in the first stages of Endochondral Ossification.
Chondroblasts
What do Chondroblasts secrete, and why, during endochondral ossification?
- BMP (bone morphogenetic protein) to facilitate growth
- Ihh (Indian hedgehog homolog) to induce further secretion BMP (positive feedback)
Chondroblasts produce a madrix that forms _________
Hyaline cartilage
What do the chondrocytes secrete after they enlarge?
alkaline phosphatase
Describe the steps in endochondral ossification from the point in which Hydroxyapatite deposits within the cartilaginous matrix.
- Cartilage cells die by apoptosis and form spaces called lacunae
- Capillaries vascularize the calcified cartilage
- These capillaries carry both hemopoietic cells and osteoprogenitor cells into the cartilage model
- the hemopoietic cells become the bone marrow
- Osteoblasts arise from mesenchymally-derived osteoprogenitor cells, and deposit bone matrix, replacing the cartilage.
What is Achondroplasia?
The premature ossification of epiphyseal plates
How does remodeling of the bone happen?
Differential deposition and resorption of bone by the osteoblasts and osteoclasts, respectively
What are osteoblasts derived from?
osteoprogenitor cells
What are osteoclasts derived from? and how are they activated?
Fused mononuclear hemopoietic progenitor cells and activated by cytokine signaling from marrow stromal cells.
What are the 3 bones of the shoulder?
Scapula, Clavicle, Humerus
What are the 4 joints of the shoulder?
Glenohumeral, acromioclavicular, sternoclavicular, scapulothoracic
What is the hole at superior to the spine of the scapula called?
Scapular foramen
What are the two ends of the clavicle bone called?
Acromial and sternal
On which end of the clavicle is the conoid tubercle?
Distal end
What is the most frequently broken bone in the body?
The clavicle
What is the difference between the anatomical and surgical necks of the humerus?
Anatomical neck is the narrow ring between the head and tubercles.
Surgical neck is an empirically designated region inferior to the tubercles, that is subject to fractures.
What type of joint is the glenohumeral joint?
Ball and socket
What stabilizes the glenohumeral joint?
The rotator cuff muscles
What structure does the transverse humeral ligament span?
Bicipital groove
What is a bursa?
Connective tissue sacs filled with lubricating fluid
What are the two bursa in the glenohumeral joint?
The subacromial and subdeltoid
What are the four nerves of the superficial back?
Suprascapular, axillary, accessory, dorasal scapular
