Cleavage in first week of development

Cleavage

It is a series of mitotic divisions of the zygote.

Cytoplasm of zygote is successively cleavage (partitioned  ) to form a blastula consisting of increasingly smaller blastomeres (2-cell, 4-cell, 8-cell and so on)

Blastomeres are considered totipotent (capable of forming a complete embryo) upto the 4-8 cell stage (important when considering monozygotic twinning )

Blastomeres form a morula by undergoing compaction that is tight junctions are formed between the cells in the outer cell mass , thereby sealing off the inner cell mass . uvomorulin a glycoprotein found on the surface of blastomeres is involved in compaction

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The diaphragms in the body

The diaphragms in the body are
1. diaphragma sellae
2. oral diaphragm (mylohyoid muscle)
3.supra pleural membrane (sibson's fascia )
4.the diaphragm
5. pelvic diaphragm
6. urogenital diaphragm

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Summary of pericardial sinuses both transverse sinus and oblique sinus

Sinuses of pericardium

Pericardial sinuses are potential space within the serous pericardiam .

There are two pericardial sinuses: transverse and oblique.

Oblique sinus

Definition :

It is the cul-de-sac behind the left atrium and is closed on all sides except below .

It is placed between parietal and visceral layer of pericardium

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 Shape:

 Inverted ‘J’ shaped

Boundaries:

Anteriorly : left atrium and visceral layer of serous pericardium

Posteriorly :  parietal layer of pericardium and fibrous pericardium

Right side : right pair of pulmonary veins and inferior vena cava

Left side : left pair of pulmonary veins

Above : upper margin of left atrium

Inferiorly : open

Special note:

The roof of oblique sinus and floor of transverse sinus is separated by upper margin of

the left atrium only , along which a bilaminar fold of serous pericardium extends from the

upper right to the upper left pulmonary veins

Development:

It develops as an effect of absorption of 4 pulmonary veins into the left atrium.

Function of oblique sinus:

 The oblique sinus permits the distension of left atrium during return of oxygenated

blood in it from the lungs.

Transverse sinus

Definition :

It is a transverse passage between two tubular reflections of serous pericardium and is lined by visceral layer only. It is an inter-visceral space.

Boundaries :

In front : ascending aorta and pulmonary trunk enclosed in a single tube of serous pericardium because both are developed from the truncus arteriosus

Behind intra-pericardial part of superior vena cava and upper margin of left atrium

Above bifurcation of pulmonary trunk

Below upper surface of left atrium

Development:

it is developed after degeneration of the central cells of the dorsal mesocardium .

Summary of transverse sinus of pericardium with clinical anatomy

Transverse sinus

Definition :

It is a transverse passage between two tubular reflections of serous pericardium and is lined by visceral layer only. It is an inter-visceral space.

Boundaries :

In front : ascending aorta and pulmonary trunk enclosed in a single tube of serous pericardium because both are developed from the truncus arteriosus

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Behind intra-pericardial part of superior vena cava and upper margin of left atrium

Above bifurcation of pulmonary trunk

Below upper surface of left atrium

Development:

it is developed after degeneration of the central cells of the dorsal mesocardium .

Summary of oblique sinus of pericardium with clinical anatomy

Oblique sinus

Definition :

It is the cul-de-sac behind the left atrium and is closed on all sides except below .

It is placed between parietal and visceral layer of pericardium

 Shape:

 Inverted ‘J’ shaped

Boundaries:

Anteriorly : left atrium and visceral layer of serous pericardium

Posteriorly :  parietal layer of pericardium and fibrous pericardium

Right side : right pair of pulmonary veins and inferior vena cava

Left side : left pair of pulmonary veins

Above : upper margin of left atrium

Inferiorly : open

Special note:

The roof of oblique sinus and floor of transverse sinus is separated by upper margin of

the left atrium only , along which a bilaminar fold of serous pericardium extends from the

upper right to the upper left pulmonary veins

Development:

It develops as an effect of absorption of 4 pulmonary veins into the left atrium.

Function of oblique sinus:

 The oblique sinus permits the distension of left atrium during return of oxygenated

blood in it from the lungs.

Summary of Hepato-renal recess/ Pouch of Morison

Hepato-renal recess/ Pouch of Morison

Definition:

The hepatorenal recess^[1] (subhepatic recess, pouch of Morison or Morison's pouch) is the space that separates the liver from the right kidney. As a potential space, the recess is not filled with fluid under normal conditions.

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Boundaries :

Anteriorly :

·         inferior surface of right lobe of liver and gall bladder

Posteriorly :

·         right suprarenal gland

·         Upper part of right kidney

·         2^nd part of duodenum

·         Hepatic flexure of colon

·         Transverse mesocolon

Superiorly

·         Inferior layer of coronary ligament

Inferiorly

·         Opens into general peritoneal cavity

Clinical anatomy :

 However, fluid can collect in this space in circumstances where the abdomen fills with fluid, such as mostly ascites and hemo peritoneum. This fluid may be seen on ultrasound or computed tomography (CT scan).

 The intraperitoneal fluid, be it blood, ascites, or dialysis, collects in this space and may be visualized, most commonly via ultrasound or computed tomography (CT) scanning. As little as 30 or 40 ml of fluid in the abdominal cavity may be visualized in this space.

Early visualization of fluid in the hepatorenal recess on FAST scan may be an indication for urgent laparotomy

Pelvic splanchnic nerve : easy and brief discussion

Pelvic splanchnic nerve :

Pelvic splanchnic nerves is also known as  nervi erigentes

Pelvic splanchnic nerves are splanchnic nerves that arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the hindgut.

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The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the internal organs, carrying fibers of the autonomic nervous system (visceral efferent fibers)   as well as sensory fibers from the organs (visceral afferent fibers. All carry sympathetic fibers except for the pelvic splanchnic nerves, which carry parasympathetic fibers.

      The parasympathetic nervous system is referred to as the craniosacral outflow;

       the pelvic splanchnic nerves are the sacral component.

       They are in the same region as the sacral splanchnic nerves,

        which arise from the sympathetic trunk and provide sympathetic efferent fibers.

Splanchnic nerve carrying sympathetic fibres  

·         Cardiopulmonary nerves

·         Thoracic splanchnic nerves (greater, lesser, and least)

·         Lumbar splanchnic nerves

·         Sacral splanchnic nerves

    Splanchnic nerve carrying parasympathetic fibres  

·         Pelvic splanchnic nerve

Plexuses and pelvic splanchnic nerves :

1.    Sacral plexus

2.    Inferior hypgastric plexus

3.    Superior hypogastric plexuses

4.    Inferior mesenteric plexuses

·         Formation of  Pelvic splanchnic nerves

The pelvic splanchnic nerves arise from the anterior rami of the sacral spinal nerves S2-S4 and enter the sacral plexus. They travel to their side's corresponding inferior hypogastric plexus, located bilaterally on the walls of the rectum.

Functional component of pelvic splanchnic nerve :

1.    GVA: general visceral afferent : collect sensation from pelvic viscera and hindgut

2.    GVE: general visceral efferent : innervate smooth muscle cells and gland

Distribution of

1.    GVA: general visceral afferent: location of cell body in dorsal root ganglia of 2-4 sacral spinal nerve . central process enter the cord by posterior nerve root .

Two fates of GVA fibres :    

                                            i.            some GVA fibres make local synaptic connections .  they are responsible for bladder reflexes

                                          ii.            Other GVA fibres   collect sensory information from pelvic viscera and convey these information to higher cortical center .         

SN: both sympathetic and parasympathetic pathway collect pain sensation from urinary bladder and rectum                                        

2.    GVE: general visceral efferent

Pre-ganglionic  fibres arises from pre-ganglionic neurons which are located in the 2-4 sacral segments of spinal cord

Then pre-ganglionic fibres leave the spinal cord through anterior root of spinal nerve, trunk of spinal nerve then leave the spinal nerve when they exit anterior sacral foramina  and form pelvic splanchnic nerves . The preganglionic fibres of pelvic splanchnic nerves synapse with  Intrinsic ganglia of descending and sigmoid colon, rectum and other the pelvic viscera  

 these fibres innervate smooth muscles of hindgut and urinary bladder

Three distribution of pelvic splanchnic nerve

1.      Anterolateral branch

2.      Branches join with hypogastric nerves

3.      Superolateral branch

Distribution of three branches

1.      Anterolateral branch : join with inferior hypogastric plexuses and then distributed into pelvic viscera

2.      Branches join with hypogastric nerves: after joining with the hypogastric nerve these branch ascend and join with superior hypogastric plexuses and distributed in to the inferior mesenteric artery  

3.      Superolateral branch : it passes directly into the tissue of the retroperitoneum and the mesentery of sigmoid and descending colon

Functions of pelvic splanchnic nerve :

1.    Pelvic splanchnic nerve  the innervation of smooth muscle cells of the pelvic and genital organs.

2.    It relaxes the smooth muscle cells of sphincter vesicae but contract detrusor muscle (smooth muscle cells) of urinary bladder   

3.    It influences motility in the rectum 

4.    In the distal 1/3 of the transverse colon, and through the sigmoid and rectum, and the cervix  in females,

5.     The pelvic splanchnic nerves collect the sensation of pain from the hindgut & pelvic organ but  the rest of the proximal gastrointestinal tract sensation is collected  by the vagus nerve .

6.      Vasodilator fibres to the erectile tissue of the penis and clitoris

7.      Secretomotor fibres to the hindgut

Pelvic splanchnic nerve : easy and brief discussion

Pelvic splanchnic nerve :

Pelvic splanchnic nerves is also known as  nervi erigentes

Pelvic splanchnic nerves are splanchnic nerves that arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the hindgut.

The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the internal organs, carrying fibers of the autonomic nervous system (visceral efferent fibers)   as well as sensory fibers from the organs (visceral afferent fibers. All carry sympathetic fibers except for the pelvic splanchnic nerves, which carry parasympathetic fibers.

      The parasympathetic nervous system is referred to as the craniosacral outflow;

       the pelvic splanchnic nerves are the sacral component.

       They are in the same region as the sacral splanchnic nerves,

        which arise from the sympathetic trunk and provide sympathetic efferent fibers.

Splanchnic nerve carrying sympathetic fibres  

·         Cardiopulmonary nerves

·         Thoracic splanchnic nerves (greater, lesser, and least)

·         Lumbar splanchnic nerves

·         Sacral splanchnic nerves

    Splanchnic nerve carrying parasympathetic fibres  

·         Pelvic splanchnic nerve

Plexuses and pelvic splanchnic nerves :

1.    Sacral plexus

2.    Inferior hypgastric plexus

3.    Superior hypogastric plexuses

4.    Inferior mesenteric plexuses

·         Formation of  Pelvic splanchnic nerves

The pelvic splanchnic nerves arise from the anterior rami of the sacral spinal nerves S2-S4 and enter the sacral plexus. They travel to their side's corresponding inferior hypogastric plexus, located bilaterally on the walls of the rectum.

Functional component of pelvic splanchnic nerve :

1.    GVA: general visceral afferent : collect sensation from pelvic viscera and hindgut

2.    GVE: general visceral efferent : innervate smooth muscle cells and gland

Distribution of

1.    GVA: general visceral afferent: location of cell body in dorsal root ganglia of 2-4 sacral spinal nerve . central process enter the cord by posterior nerve root .

Two fates of GVA fibres :    

                                            i.            some GVA fibres make local synaptic connections .  they are responsible for bladder reflexes

                                          ii.            Other GVA fibres   collect sensory information from pelvic viscera and convey these information to higher cortical center .         

SN: both sympathetic and parasympathetic pathway collect pain sensation from urinary bladder and rectum                                        

2.    GVE: general visceral efferent

Pre-ganglionic  fibres arises from pre-ganglionic neurons which are located in the 2-4 sacral segments of spinal cord

Then pre-ganglionic fibres leave the spinal cord through anterior root of spinal nerve, trunk of spinal nerve then leave the spinal nerve when they exit anterior sacral foramina  and form pelvic splanchnic nerves . The preganglionic fibres of pelvic splanchnic nerves synapse with  Intrinsic ganglia of descending and sigmoid colon, rectum and other the pelvic viscera  

 these fibres innervate smooth muscles of hindgut and urinary bladder

Three distribution of pelvic splanchnic nerve

1.      Anterolateral branch

2.      Branches join with hypogastric nerves

3.      Superolateral branch

Distribution of three branches

1.      Anterolateral branch : join with inferior hypogastric plexuses and then distributed into pelvic viscera

2.      Branches join with hypogastric nerves: after joining with the hypogastric nerve these branch ascend and join with superior hypogastric plexuses and distributed in to the inferior mesenteric artery  

3.      Superolateral branch : it passes directly into the tissue of the retroperitoneum and the mesentery of sigmoid and descending colon

Functions of pelvic splanchnic nerve :

1.    Pelvic splanchnic nerve  the innervation of smooth muscle cells of the pelvic and genital organs.

2.    It relaxes the smooth muscle cells of sphincter vesicae but contract detrusor muscle (smooth muscle cells) of urinary bladder   

3.    It influences motility in the rectum 

4.    In the distal 1/3 of the transverse colon, and through the sigmoid and rectum, and the cervix  in females,

5.     The pelvic splanchnic nerves collect the sensation of pain from the hindgut & pelvic organ but  the rest of the proximal gastrointestinal tract sensation is collected  by the vagus nerve .

6.      Vasodilator fibres to the erectile tissue of the penis and clitoris

7.      Secretomotor fibres to the hindgut

Pelvic splanchnic nerve : Summary

Pelvic splanchnic nerve :

Pelvic splanchnic nerves is also known as  nervi erigentes

Pelvic splanchnic nerves are splanchnic nerves that arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the hindgut.

The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the internal organs, carrying fibers of the autonomic nervous system (visceral efferent fibers)   as well as sensory fibers from the organs (visceral afferent fibers. All carry sympathetic fibers except for the pelvic splanchnic nerves, which carry parasympathetic fibers.

      The parasympathetic nervous system is referred to as the craniosacral outflow;

       the pelvic splanchnic nerves are the sacral component.

       They are in the same region as the sacral splanchnic nerves,

        which arise from the sympathetic trunk and provide sympathetic efferent fibers.

Splanchnic nerve carrying sympathetic fibres  

·         Cardiopulmonary nerves

·         Thoracic splanchnic nerves (greater, lesser, and least)

·         Lumbar splanchnic nerves

·         Sacral splanchnic nerves

    Splanchnic nerve carrying parasympathetic fibres  

·         Pelvic splanchnic nerve

Plexuses and pelvic splanchnic nerves :

1.    Sacral plexus

2.    Inferior hypgastric plexus

3.    Superior hypogastric plexuses

4.    Inferior mesenteric plexuses

·         Formation of  Pelvic splanchnic nerves

The pelvic splanchnic nerves arise from the anterior rami of the sacral spinal nerves S2-S4 and enter the sacral plexus. They travel to their side's corresponding inferior hypogastric plexus, located bilaterally on the walls of the rectum.

Functional component of pelvic splanchnic nerve :

1.    GVA: general visceral afferent : collect sensation from pelvic viscera and hindgut

2.    GVE: general visceral efferent : innervate smooth muscle cells and gland

Distribution of

1.    GVA: general visceral afferent: location of cell body in dorsal root ganglia of 2-4 sacral spinal nerve . central process enter the cord by posterior nerve root .

Two fates of GVA fibres :    

                                            i.            some GVA fibres make local synaptic connections .  they are responsible for bladder reflexes

                                          ii.            Other GVA fibres   collect sensory information from pelvic viscera and convey these information to higher cortical center .         

SN: both sympathetic and parasympathetic pathway collect pain sensation from urinary bladder and rectum                                        

2.    GVE: general visceral efferent

Pre-ganglionic  fibres arises from pre-ganglionic neurons which are located in the 2-4 sacral segments of spinal cord

Then pre-ganglionic fibres leave the spinal cord through anterior root of spinal nerve, trunk of spinal nerve then leave the spinal nerve when they exit anterior sacral foramina  and form pelvic splanchnic nerves . The preganglionic fibres of pelvic splanchnic nerves synapse with  Intrinsic ganglia of descending and sigmoid colon, rectum and other the pelvic viscera  

 these fibres innervate smooth muscles of hindgut and urinary bladder

Three distribution of pelvic splanchnic nerve

1.      Anterolateral branch

2.      Branches join with hypogastric nerves

3.      Superolateral branch

Distribution of three branches

1.      Anterolateral branch : join with inferior hypogastric plexuses and then distributed into pelvic viscera

2.      Branches join with hypogastric nerves: after joining with the hypogastric nerve these branch ascend and join with superior hypogastric plexuses and distributed in to the inferior mesenteric artery  

3.      Superolateral branch : it passes directly into the tissue of the retroperitoneum and the mesentery of sigmoid and descending colon

Functions of pelvic splanchnic nerve :

1.    Pelvic splanchnic nerve  the innervation of smooth muscle cells of the pelvic and genital organs.

2.    It relaxes the smooth muscle cells of sphincter vesicae but contract detrusor muscle (smooth muscle cells) of urinary bladder   

3.    It influences motility in the rectum 

4.    In the distal 1/3 of the transverse colon, and through the sigmoid and rectum, and the cervix  in females,

5.     The pelvic splanchnic nerves collect the sensation of pain from the hindgut & pelvic organ but  the rest of the proximal gastrointestinal tract sensation is collected  by the vagus nerve .

6.      Vasodilator fibres to the erectile tissue of the penis and clitoris

7.      Secretomotor fibres to the hindgut