Spinal cord at a glance

Spinal Cord & Nerves

This is the viscera of spinal cord and spinal meninges

1.         Anatomical points:

             I.         anteriror median fissure lies anteriorly

          II.      cauda equine lies inferiorly

2.         length : 45cm                    wide 2.5 cm

3.          Extension of spinal cord:

   Adult: at the level of foramen magnum to lower border of 1^st lumbar vertebra

   Children: at the level of the foramen magnum to the 3^rd lumber vertebra

4.         Terminal part of sub-arachnoid space of the spinal cord : lower border of 2^nd sacral vertebra

5.         termination of filum terminalis: at the 1^st coccyx

External feature of spinal cord :

i)                    anteriorly : anterior median fissure

ii)                  posteriorly : posterior median septum

iii)                inferiorly : filum terminalis and cauda equine

iv)                two enlargement in cervical and lumbar region

v)                  external surface is covered by spinal meninges : outer meningeal dura mater, middle arachnoid mater and  inner pia mater

vi)                ventral roots, dorsal roots and dorsal root ganglia and spinal nerve

6.         How many enlargement present within the spinal cord and why?

i)                    Cervical enlargement: extend from the foramen magnum to 1^st thoracic vertebra. Supply upper limb

ii)                  Lumbar enlargement: extend from thoracic 10^th to 12^th vertebra. Supply lower limb.

7.         What is spinal segment?

 Ans: Part of the spinal cord to which one pairs of spinal nerve is attached.

8.         How many spinal segments present in the spinal cord? – 31 spinal segments

9.         What is conus medullaris? – cone shaped terminal part of spinal cord

 1.         What is filum terminalis ? – it is the prolongation of pia mater which extend from the cunus medullaris to 1^st coccyx

2.         What is cauda equine: the lumbar and sacral roots below the termination of spinal cord continue as a leash of nerve roots known as cauda equine.

3.         What is legamentum denticulate: it is the thickening of pia mater situated on either side of spinal cord between nerve roots. (Figure ellis 364)

Spinal nerve

How many Spinal nerves present in our body? Number: 31 pairs. 8 cervical spinal nerve, 12 thoracic spinal nerve, 5 lumbar spinal nerve, 5 sacral spinal nerve and 1 coccygeal spinal nerve

How a spinal nerve is formed? :  Spinal nerve form by union of ventral and dorsal nerve roots

Location of spinal nerve: within the intervertebral foramen

Exit : C1-C7 spinal nerves exit ABOVE C1-C7 vertebrae

                         C8 spinal nerve projects below C7 vertebra

                         T1-S5 spinal nerves project BELOW T1-S5 vertebrae

 Branches of a Spinal Nerve:

                        1. dorsal ramus – supply deep muscles and skin of back

                        2. ventral ramus – supply upper and lower extremities, ventrolateral trunk

                        3. meningeal branch - back into the spinal column

                        4. rami communicantes - for autonomic nerve fibers

Type of spinal nerves: they are mixed nerve (both sensory and motor ).

Component: GSA (general somatic afferent –carry impulse from periphery to CNS) and GSE( general somatic efferent- impulse goes from CNS to skeletal muscle)

Plexus of spinal nerve: plexus of spinal nerve is formed by ventral rami of different spinal nerves. There are four spinal nerve plexus  present within the body.

Name of plexus	Formation	Supplied area	Important nerve of the plexus
1. cervical plexus	ventral rami of C1-C4 with some C5	a. muscles/skin of head, neck, some shoulder b. phrenic nerve - diaphragm muscle (breathing)	phrenic nerve -
2. brachial plexus	ventral rami of C5-C8 and T1	Upper limb and shoulder	Axillary N, musculocutanous  N, Radial N, median N, Ulnar N
3. lumbar plexus	- ventral rami of L1-L4	a. abdominal wall, genitals, part of lower limb	Femoral N, Obturator N
4. sacral plexus	ventral rami of L4-L5 and S1-S4	a. buttocks, perineum, part of lower limb b. sciatic nerve	Sacral n- largest nerve of body,  pudendal n, Sup and inf Gluteal n

                       

 Dermatomes: area of skin is supplied by single spinal nerve

           

Internal feature of spinal cord:

Inner grey matter contains a central canal. Parts of grey matter, ant horn and pos horn and lateral horn only in thoracic and lumbar region

Grey matter contain motor and internuncial neuron

Parts of outer white matter: 1. anterior (ventral) column

                        2. posterior (dorsal) column

                        3. lateral (intermediate) column

white matter contain ascending and descending tracts:

fasciculi/tracts –they are collection  axon bundles within the CNS. They are two types:                                a. ascending tracts – carry sensory impulse to the brain. Spinothalamic tract

            b. descending tracts – carry motor impulse from brain to the effector organ (skeletal muscle). corticospinal tract

Important tract within the spinal cord :

ASCENDING TRACTS (SENSORY)
anterior (ventral) spinothalamic	touch and pressure to thalamus
lateral spinothalamic tract	pain & temperature to thalamus
fasciculus gracilis	touch, 2-pt. discrimination,
fasciculus cuneatus	conscious proprioception,      vibration
posterior spinocerebellar                                  anterior spinocerebellar	subconscious proprioception

DESCENDING TRACTS (MOTOR)
lateral corticospinal                                          anterior corticospinal tract	Carry motor output from cortex to motor neuron of ant. Grey horn which stimulate the skeletal muscles

Blood supply: one ant and two posterior spinal arteries. Other branches: ascending cervical a, pos intercostals a, and the lumbar a

Vein: ant and pos spinal vein.

Development : caudal part of neural tube (neuroectodarm)

Cell cycle: easy and brief description

Cell cycle

Cyclic changes of a cell involving interphase and mitosis is known as the cell cycle.

There are two stages of cell cycle

1. Inter-phase : divided into three phases:

                            G1 Phase

                             S phase and

                              G2 phase

2. Mitosis

Interphase

The phase between two mitoses is called inter-phase

Phase	Duration	Synthesize
The G1 phase it began at the end of M phase	longest duration the most variable phase of the cell cycle	the RNA and protein synthesis
S phase	7 to 10 hrs	DNA synthesis
G2 phase	1hr	Accumulation of energy (for mitosis) Synthesis of tubulin (for formation of mitotic microtubules) Synthesize of chromosomal non-histone proteins

G0: Some terminally differentiated cells leave the cell cycle after the M phase and enter Go phase

Example : neuron

Trigone of urinary bladder

Trigone of urinary bladder: it is situated interior of base of urinary bladder 

Boundary:

Distance between ureter to ureter 2.5 cm

Distance between ureter to urethra 2.5 cm

But in distended bladder it is 5 cm

Inter-ueteric fold is formed by continuity of the longitudinal muscles of ureters across the bladder

Ureteric orifice close by distension of urinary bladder but it open rhythmically in response to ureteric peristalsis and a jet of urine injected into bladder (4 or 5 times a minute normally )

Trigone contain two group of muscles

Superficial trigone muscle :

1.       a triangular layer of muscles, morphologically distinct component of the trigone

2.       it contain small diameter smooth muscle cells

3.       it is a thin muscle layer except at interureteric fold and urethra-ureteric fold where it is thicken

4.       in both sex it is continuous with muscles of ureter and urethra and in male it is also continuous with muscles of ejaculatory duct near the opening  

5.       different from other part of urinary bladder , it is rich in sympathetic supply

Deep trigone detrusor muscle

Sympathetic supply of urinary bladder:

1.       Vasomotor

2.       Inhibit detrusor muscle

1.       Motor to superficial trigone muscle and muscles of bladder neck in male

Parasympathetic supply of urinary bladder

1.       Contraction of detrusor muscle

2.       Sense of filing – travel by parasympathetic system then spinal cord then by tract of gracile

3.       But pain sensation travel by both sympathetic and parasympathetic then lateral spinothalamic tract

Surface anatomy /living anatomy : important structures with easy points for drawing

Living Anatomy

1.      Frontal sinus

1^st point- On the nasion

2^nd point- 2.5 cm above the 1^st point.

3^rd point- At the junction of the medial 1/3 and the lateral 2/3 of the supra- orbital margin.

Join the points.

Related information:

Drainage areas: middle meatus of nasal cavity

Lining epithelium: pseodustratified ciliated columnar epithelium 

Functions of sinus: resonance of voice, lightening the wt of bone 

What is the name of sinus containing bones: pneumatic bone

2.      Parotid duct 

1^st point: just in front and below the tragus

2^nd point : between the ala of nose and the sharp margin of the upper lip

Join the 1^st and 2^nd point. The middle third of this line is parotid duct

Related questions:What type of gland it is? Ans: exocrine gland (because it has a duct)

According to the nature of secretion: it is pure serous in nature

Parts of this gland: Parenchyma (glandular portion )and stroma (connective tissue)

Histology: Serous acini are present. (Serous acini are darkly stain and cells of acini contain round nuclei)

Duct is present

Development of glands: Parenchyma: endodermal in origin. Stroma: mesodermal in origin

Opening of parotid duct: at the vestibule of mouth opposite the crown of 2^nd molar teeth

3.      Isthmus of thyroid gland

1^st point:  1.25 cm below the cricoid cartilage

2^nd point: 1.25cm below the 1^st point

Draw two 1.25 cm long horizontal lines along the 1^st and 2^nd point.

 1.      Sternal angle : it is an important bony landmark

It helps counting the number of ribs because the 2^nd costal cartilages articulate at this level

It separates the superior mediastinum to inferior mediastinum

It is correspond with lower border of T4 vertebra

2.      Rt border of heart

1^st point: On   the upper border   of the right 3^rd costal cartilage about 2.5 cm from the median   plane.

2^nd point: on   the right 6^th costal cartilage about 2.5 cm from the median plane

Join these two points by a convex line towards the right.

SN: (The maximum convexity of which lies at a distance of 3.25am from the median plane in the 4^th intercostal space.)

Related questions:

How it is formed?  Ans: it is formed by right atrium

3.      left border of heart

1) 1^st    Point – On the lower border of the left 2^nd costal cartilage about 2.5 cm from the median plane.

2) 2^nd   point- At the apex beat left 5^th intercostal space just medial to mid-clavicular line Join   these two points by line with convexity directed upwards and to the left.

Related questions:

How it is formed? Ans: it is formed by left ventricle of the heart

4. Lower border of the Heart

1^st point: on   the right 6th costal cartilage about 2.5 cm from the median plane

2^nd   point-At the apex beat left 5^th intercostal space just medial to mid-clavicular line

Apex of the   Heart

It is situated in the left 5^th intercostal space just medial to midclavicular   line.

Related questions:  How it is formed?

Ans: It is formed by only left ventricle of the heart.

Apex of the Lung

1^st point – rt/lt  sternoclavicular   joint

 2^nd point –at the junction of medial 1/3 and lateral 2/3 of clavicle

Join these two points & the summit of the curve being situated in the neck about 2.5cm above the medial   third of clavicle.    

by which structure  apex of the lung is covered?

Ans:    The apex of the lung is covered by cervical pleura (part of parietal pleura) and supra-pleural membrane

What is suprapleural membrane?

Ans: it is formed by endothoracic fascia

Attachment : internal border of 1^st rib and transverse process of C7                                                                                                                                                                                                                                                                    

Arch of the Aorta

1) 1^st point –On the right end of the   sternal angle.

2) 2^nd point –On the   centre of the manubrium   sterni

3)3^rd point- sternal end of left 2^nd costal cartilage 

Join the points by a curved line which represents the outer border of the arch of aorta; then the inner   border is drawn   below  &  paralled to it about 2.5 cm apart  .

Importance points :  It is the continuation of ascending aorta and It is continued as descending thoracic aorta

Related questions : What are the branches of arch of aorta?

1. brachiocephalic artery/ trunk : right common carotid and right subclavian artery
2. left common carotid artery
3. left subclavian artery

What is the type of these arteries?  Ans : elastic artery.

Why they known as elastic artery? They contain large numbers of elastic lamina within the tunica media. 

7.      Trans- pyloric plane

It is indicated by a transverse line drawn midway between the jugular notch and the top of the symphysis pubis (or roughly in between the xiphisternal junction and the umbilicus.)

 The following important structures are situated opposite this plan:-

1)      Pyloric part of the stomach.

2)      Fundus of the gall-bladder.

3)      Hilum of the kidneys.

4)      Tip of the 9^th costal cartilage.

5)      Origin of the superior mesenteric artery.

6)      Lower border of the body of the 1^st lumbar vertebra or upper border of its spine.

7)      Lower end of the spinal cord and beginning of the filum terminale.

Trans-tubercular plane: It is indicated by a transverse line of  the trunk at the level of the tubercle of the iliac crest. It cuts the upper border of the body and spine of the 5^th lumbar vertebra.

   Fundus of gall bladder : it is marked at anterior abdominal wall at tip of the 9th costal cartilage (depression in anterior abdominal wall / where transpyloric plane crosses the right costal margin)

9.      Liver

Upper border is marked by joining the following points.

1st point:  in left 5th intercostal space just medial to midclavicular line .

2nd point:  at xiphisternal joint.

3rd point: at upper border of right 5th costal cartilage in right mid-clavicular line 

Lower border:

 4^th point  at tip of the right 9^th  costal cartilage .

5^th point : 1^st point of upper border (left 5th intercostal space just medial to midclavicular line )

Right lateral border: join 3^rd point to 4^th point

Situation of liver:

1.      Right hypochondrium

2.      Epigastric region

3.      Left hypochondrium

4.      Right lumbar region

10.  McBurney’s point : at 1^st draw a line from the right anterior superior iliac spine to umbilicus

Then draw a point  at the junction of lateral 1/3 & medial 2/3 of line, and this is the McBurney’s point.

1 Arteria dorsalis pedis

Arteria dorsalis pedis :

1^st point: in front of the ankle joint midway between medial and lateral malleolus

2^nd point: at the proximal end of the 1^st intermetatarsal space

Join the points by a straight line

Related information: It is the continuation of anterior tibial artery 

 1.      Brachial artery

1)      1^st point- at the junction of anterior 1/3 and posterior 2/3 of the lateral wall of the axilla

2)      2^nd point- 2.5 below and medial to the tendon of the biceps brachii.

Join the points by a straight line.

Related information:  brachial artery is the continuation of axillary artery.

Branches of brachial artery:

1. Profunda Brachii.
2. Superior Ulnar Collateral.
3. Inferior Ulnar Collateral
4. Nutrient
5. Muscular
6. Terminal branches: Radial and ulnar artery

2.      Radial artery

1^st point- 2.5 below and medial to the tendon of the biceps brachii .

2^nd point- In front of the wrist between the tendon of the flexor carpi radialis medially and the lower part of the anterior border of the radius laterally.(Here, practically feel the pulsation of the artery and put the point over it).

   Join the points by a line with slight outwards convexity at the upper part.

Related informations: Branches radial artery : In the Forearm:

1.   Radial Recurrent artery,
2.   Muscular artery 
3.   Superficial Volar artery

 At the Wrist: Dorsal Carpal artery

    In the hand:

1. Princeps Pollicis.
2. Volaris Indicis Radialis.

3.      Median cubital vein

1^st point : 2.25 cm above from the medial epicondyle

2^nd point : 2.25 cm below from the lateral epicondyle

Join these points by an oblique line

Why median cubital vein choose for intravenous injection?

Ans : it is superficial and fixed on underlying fascia.

Related informations:

Name of the superficial vein of upper limb: cephalic vein, basilic vein, median cubital vein

Name of the deep vein of upper limb: axillary, brachial, ulna and radial vein