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