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

Portal circulation: easy and brief description

Portal circulation: any part of the systemic circulation in which blood passage through two sets of capillary before draining to the heart

Types :

1. Arterial  portal system, EX: renal portal system

Heart >  artery > 1^st set capillary (at renal glomeruli) > arteriole > 2^nd set capillary (at capillary plexus surrounding the proximal and distal convoluted tubule of nephron )  > vein > heart

2. Venous portal system : EX: hepatic portal system

Heart > artery > 1^st set capillary (GIT) > vein  > 2^nd set capillary (liver) > vein > heart . 

What is the importance of portal circulation? 

Ans: if we want to transfer  blood of a particular region to other particular region for purpose then we need portal circulation 

Example: Gut and liver

gut blood vessels rich in nutrient , and nutrient need to metabolized  in liver so, gut veins are not directly drain into IVC , at first it goes to liver then drain into IVC 

Example:  Hypothalamus and pituitary 

The releasing hormones of hypothalamus must transfer to the anterior pituitary and anterior pituitary is stimulated and secretions

of anterior pituitary circulate through systemic circulation 

Development of spinal cord (alar and basal plate) : easy and brief description

Development of spinal cord 

Nervous tissue (brain and spinal cord ) is developed from neuroectoderm 

Neuroectoderm is developed from ectoderm 

Part of ectoderm is thickened and form neuroectoderm 

Neuroectoderm detouch from the ectoderm and formed a tube , know as neural tube.

Its cranial end dilated and formed brain and its caudal end remain narrow formed spinal cord .

What is the microscopic structure of neural tube? 

Ans: It is formed by simple columnar epithelium known as neuroepithelium .

From neuroepithelium new neuroblasts are formed by mitosis, they formed a separate layer around the neural tube known as mantle layer .

 Processes, axon and dendrites are begin grow from neuroblast , makes a new later around the mantle layer, known as marginal layer

Again mantle layer is divided into four part.Two ventral part, known as basal plates and

 two dorsal part known as alar part. 

These parts are separated by a sulcus known as sulcus limitans 

Two basal plates are separated by roof plate 

Two alar plates are separated by floor plate 

Basal plates are formed anterior horn of gray matter 

Alar plates are formed posterior horn of gray matter 

So, whole gray matter is came from mantle layer 

white matter is came from marginal layer 

and origin neuroepithelium is converted into ependyma of central canal 

And lumen of neural tube converted into central canal 

Optic nerve: easy and brief discussion

Optic nerve: 

Formation: by axon of ganglionic cells of retina 

Functional component: special somatic afferent 

Peculiarities of optic nerve: 

1. it is the prolongation of diencephalon 

2. it is the white matter of brain 

3. it is covered by three meninges of brain 

4. its myelination is derived from oligodendrocyte so it is devoid of neurolemma sheath and no regeneration 

5. pia mater project into nerve and carry blood vessels with it 

Blood supply of optic nerve: superior hypophyseal artery, ophthalmic artery and posterior ciliary artery 

parts of optic nerve with length :

1. intra orbital part : 25 mm
2. canalicular part : 5 mm 
3. intra cranial part  : 10 mm

Total length : 4 cm 

Intra orbital part is longer so eyeball can move without any tension. 

Human eye: viva questions with answer

Human eye:

1. How many layers of eye present from outside to inside? 

Ans: outside to inside: fibrous coat ( sclera and cornea ) , vascular coat( iris, ciliary body, choroid , nervous coat (retina)

2. how many layers present in cornea?

Ans: outside to inside

• lining epithelium: non-keranized stratified squmous epithelium 
• Bowman's membrane 
• substantia propria 
• Descemet's membrane 
• corneal endothelium 

3. Mention the name of neurons in retina 

Ans: Rods and cone cells, Amacrine, bipolar neuron, ganglionic cells

4. How optic nerve is formed?

Ans:  by axon of ganglionic cells

5. Mention the name of muscles present within the iris ?

Ans : sphincter pupillae and dilator pupillae

6. Mention the secretomotor pathway of the lacrimal gland 

Ans: the preganlionic fibres start in the lacrimatory nucleus(lower pons)
pass through nervus intermedius
the geniculate ganglion
the greater petrosal nerve
the nerve of pterygoid canal
pterygopalatine ganglion
post ganglionic fibres from pterygopalatine ganglion passage through zygomatic nerve
zygomaticotemporal nerve
lacrimal nerve
lacrimal gland

7. Mention the content of orbital cavity.

Ans: Content of orbit

1. eyeball 
2. two fascia : orbital and bulbar fascia 
3. extraocular muscles
4. Lacrimal glands
5. Artery: ophthalmic 
6. Veins: superior and inferior ophthalmic vein 
7. Nerves: sensory : optic nerve and ophthalmic nerve (branches of trigeminal nerve)            Motor: oculomotor(3rd cranial nerve), trochlear nerve (4th cranial nerve) and abducent nerve (6th cranial nerve) 
8. Ganglion : ciliary 
9. Orbital fat 

8. Give nerve supply of extraocular muscles

Ans: SO 4 , LR 6 and rest 3
 Trochlear nerve :Superior oblique
Abducent nerve: Lateral rectus
oculomotor nerve : medial, superior and inferior rectus and inferior oblique muscle

9. Mention the name of branches of ophthalmic artery

Ans: ophthalmic artery is the branch of internal carotid artery
its branches are:

1. central artery of retina 
2. supraorbital and supratrochlear artery 
3. anterior and posterior ethmoidal artery 
4. posterior ciliary artery
5. medial palpebral artery 
6. muscular artery 
7. lacrimal artery 

10. Why cornea is transparent ? 

Ans: Cornea is transparent. Because

• it is avascular 
• melanin absent in corneal epithelium
• in substantia propria, bundles of collagen fibrils (not fibre) and long slender fibroblasts are parallel in arrangement 
• The transparency of cornea requires precise regulation of the water content of the stroma, this function regulate by corneal endothelium , if water contain of cornea reduces , it causes aggregation of collagen fibres so cornea become opaque