Internal thoracic artery with clinical anatomy and radiology

 

Internal thoracic artery

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Origin : from subclavian artery

Another name : internal mammary artery

Supply areas: thoracic wall and breast  

Branches :

Two terminal branches: superior epigastric and musculophrenic artery

Anterior intercostal arteries : two for each intercostal space. Upper six pairs arises from internal thoracic artery and 7-9^th pairs arises from musculophrenic nerves  

SN: in each intercostal space two intercostal arteries anastomoses with  collateral branches of one posterior intercostal artery .

Clinical anatomy: during pericardiocentesis, to avoid puncturing the internal thoracic vessels, insert the needle just at the lateral margin of the sternum and no more than 1 cm laterally.

mast cell : lecture note

 mast cell 

•       Mast cells contribute to homeostasis in the immune system.

•       They serve as a first line of defense against antigens entering the body due to their location in the skin and mucosa

•       Mast cells are especially important in the homeostasis of the commensal bacteria of the gut

 

•      Mast cell granules are metachromatic because of the high content of acidic radicals in the heparin glycosaminoglycan. Metachromasia is a property of certain molecules that changes the color of some basic aniline dyes (eg, toluidine blue). The structure containing the metachromatic molecules takes on a color (purple-red) different from that of the applied dye (blue).

•      Although they have similar morphology, there are at least two populations of mast cells in connective tissues. One type, called the connective tissue mast cell, is found in the skin and peritoneal cavity; these cells measure 10–12 µm in diameter and their granules contain the anticoagulant heparin. The second type, the so-called mucosal mast cell, is present in the connective tissue of the intestinal mucosa and in the lungs. These cells are smaller (only 5–10 µm) than the connective tissue mast cells and their granules contain chondroitin sulfate instead of heparin.

•       Difference between connective tissue mast cell and mucosal mast cell

Topics	connective tissue mast cell	mucosal mast cell
Another name	Also known as MCTC mast cell	Also known as MCT mast cell
Location	Skin , intestinal submucosa, breast and axillary lymph nodes	Lungs, intestinal mucosa
Granules and its internal structure	Granules with Lattice like internal structure	Granule with a scroll like internal structure
Granules contain	Tryptase and chymase	Only tryptase

However, mature mast cells are generally not thought to undergo cell division and are considered terminally differentiated. Occasionally cell division is occurred

The surface of mast cells contains Fc receptors for immunoglobulin E (IgE),

 a type of immunoglobulin produced by plasma cells. Most IgE molecules are bound

 to the surface of mast cells and blood basophils; very few remain in the plasma.

 

Mast cells originate from progenitor cells in the bone marrow. These progenitor cells circulate in the blood, cross the wall of venules and capillaries, and penetrate the tissues, 

The most important aspect of cohesin

 The most important aspect of cohesin

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It is a protein complex that forms a ring-like structure, and sister chromatids are thought to be held together by trapping within the cohesin ring.

Cohesin is formed by  multi-subunit protein complex

1.      SMC1, SMC3,

2.       RAD21 and

3.      SCC3 (SA1 or SA2

·         SMC proteins have two main structural characteristics

·         a head domain : an ATP-binding cassette with ATPase activity (formed by the interaction of the N- and C- terminals of RAD21)

·         a hinge domain that allows dimerization of SMCs.

·         The head and the hinge domains are connected to each other via long anti-parallel coiled coils. 

·         RAD21 is a protein that in humans is encoded by the RAD21 gene

·         Rad21 binds to the ATPase heads of Smc3 and Smc1 via its N- and C- terminus, 

Once RAD21 binds the SMC proteins, SCC3 can also associate with RAD21. 

Function of cohesion

1. It is used to keep the sister chromatids connected with each other during metaphase ensuring that during mitosis (and meiosis), each sister chromatid segregates to opposite poles.

•      2. It facilitates  attachment of microtubules of spindle  onto chromosomes.

3. It facilitates DNA repair by recombination.

4. Cohesin has been shown to be responsible for transcription regulation, DNA double strand break repair

Mechanism of Sister Chromatid Cohesion

•      it is not clear how the cohesin ring links sister chromatids together. There are two possible scenarios:

•      Cohesin subunits bind to each sister chromatid and form a bridge between the two.

•      cohesin has a ring structure, it is able to encircle both sister chromatids.

•      Localization of cohesin rings

•       

•      A few cohesin rings are found in chromosome arms that have AT-rich DNA sequences

•      Cohesin rings, are also located in the region surrounding the centromere,  especially in budding yeast,