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,

nucleus ambiguus

The nucleus ambiguus runs in a rostral to caudal direction in the medulla and is located in the ventrolateral reticular formation, posterior to the inferior olivary nuclear complex and anteromedial to the spinal trigeminal nucleus 
 
The rostral portion of the nucleus ambiguus gives rise to special visceral efferent fibers of the glossopharyngeal nerve, which innervate the stylopharyngeus muscle.
This muscle originates from the styloid process and descends between the internal and external carotid arteries to the upper wall of the pharynx.
Contraction of the stylopharyngeus muscle aids in raising the larynx and elevating and expanding the pharynx during swallowing.
 The nucleus ambiguus is also the source of special visceral efferent fibers of cranial nerves X and XI, which together with cranial nerve IX innervate the muscles of the pharynx and larynx.

The gastrosplenic ligament

 

The gastrosplenic ligament (also known as the ligamentum gastrosplenicum or gastrolienal ligament) is part of the greater omentum.

The gastrosplenic ligament is made of visceral peritoneum^.  It connects the greater curvature of stomach with the hilum of the spleen.

It contains the short gastric arteries, short gastric veins, the left gastroepiploic artery, and the left gastroepiploic vein

Development

Embryonically, the gastrosplenic ligament is derived from the dorsal mesogastrium

During portal  or splenic vein thrombosis, the collateral circulation establishes at various sites, the gastrosplenic ligament is one of those sites. 

Medial umbilical ligament

Medial umbilical ligament 

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They are bilateral raised ridges of parietal peritoneum in the deep aspect of the anterior abdominal wall overlying the inferior epigastric artery. 

The paired folds originate medial to the deep inguinal ring and end at the arcuate line on the posterior aspect of the anterior abdominal wall. The medial fossae  lie between the medial and lateral umbilical folds. The lateral fossae  lie laterally to the lateral umbilical folds.

The folds are 2 of the 5 umbilical folds. 

Significance

Because the lateral umbilical folds overly the inferior epigastric vessels, they are used as an important reference point for inguinal hernia  classification. Direct hernia  occur medial to the lateral umbilical folds whereas indirect hernias occur laterally.

Lateral umbilical ligament

Lateral umbilical ligaments/folds are bilateral raised ridges of parietal  peritoneum in the deep aspect of the anterior abdominal wall overlying the inferior epigastric vessels. The paired folds originate medial to the deep inguinal ring  and end at the arcuate line on the posterior aspect of the anterior abdominal wall.

 The medial fossae  lie between the medial and lateral umbilical folds. The lateral fossae lie laterally to the lateral umbilical folds.

The folds are 2 of the 5 umbilical folds.

Significance

Because the lateral umbilical folds overly the inferior epigastric vessels, they are used as an important reference point for inguinal hernia classification. Direct hernias occur medial to the lateral umbilical folds whereas indirect hernias occur laterally.

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Median umbilical ligament

The median umbilical ligament is a fibrous band located in the anterior portion of the abdomen, anterior to the urinary bladder. 

It contains the urachus, which is an embryonic remnant resulting from involution of the allantoic duct that connects the fetal urinary bladder to the umbilicus.

The median umbilical ligament is an unpaired ligamentous structure in human anatomy . It is covered by the median umbilical fold.

It extends from the apex of the urinary bladder to the umbilicus, on the deep surface of the anterior abdominal wall.

Lateral to this structure are the medial umbilical ligament and lateral umbilical ligament.

The median umbilical ligament may be used as a landmark for surgeons who are performing laparoscopy, such as laparoscopic inguinal hernia  repair.

Brain and eyeball card item 1 viva questions as per bmdc curriculum 2012

 General introduction to the nervous system, cranial cavity and orbit.

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1. Classification : anatominal and functional
2. central nervous system(CNS): and peripheral nervous system(PNS): parts
3. somatic nervous system control which organs / tissue of body, motor and sensory function : explain
4. autonomic nervous system:  control which organ / tissue of body, parts, function of sympathetic and parasympathetic system  
5.  nervous tissue:  Composition and Draw and label  
6. Neuron: Definition, draw and label, parts & classification of neuron according to polarity and according to function  with example.
7. Neuroglia: definition, Classification, draw and label, functions of each of them.  
8. Peripheral nerve: structural organization of  a peripheral nerve.(what is nerve fibre, nerve bundle, what is endoneurium, perineurium & epineurium
9. gray and white matter:  Composition, location of these in cerebrum, spinal cord and cerebellum
10. ganglia and nucleus:  Definition, example.
11. Synapse: Definition, parts, different types of synapse, How impulse passage from one neuron to other neuron?
12. Neurotransmitter:  Define, classification, function.
13. Plexus: Definition, formation, type and examples
14. Receptor: definition, classification, location
15. Reflex : definition, component of reflex arc, classification . name of normal and abnormal reflex.  
16. Cranial cavity : boundary and content of anterior, middle and posterior cranial fossa
17. Orbital cavity : boundary and content