Thursday, April 28, 2011

The Veins

General feature

Thin walls, larger lumens, venous valves, venous plexus

Two sets of veins:

Superficial vein

is a term used to describe a vein that is close to the surface of the body

Superficial veins are not paired with an artery, unlike the deep veins, which typically have an artery with the same name close by Superficial veins are important physiologically for cooling of the body. When the body is too hot the body shunts blood from the deep veins to the superficial veins, to facilitate heat transfer to the surroundings.

Deep vein

is a term used to describe a vein that is deep in the body
Deep veins are almost always beside an artery with the same name (e.g. the femoral vein is beside the femoral artery).
Collectively, they carry the vast majority of the blood back to the heart

The return of blood to the heart is assisted by the action of the skeletal-muscle pump which helps maintain the extremely low blood pressure of the venous system.
Fainting can be caused by failure of the skeletal-muscular pump. Long periods of standing can result in blood pooling in the legs, with blood pressure too low to return blood to the heart.


Systemic veins

To understand the arrangement of the veins in systemic circulation,we should regard them as three systems:

1)Cardiac veins system
2) Superior vena cava system—S.V.C and its tributaries
3) Inferior vena cava system—I.V.C and its tributaries
Every system takes charge of several regions of our body.
1)Cardiac veins system---- drain the venus blood of heart
2) Superior vena cava system--- head,neck,thorax,upper
limb
3) Inferior vena cava system--- abdoman,pelvis,lower limb


Superior vena cava system

Superior vena cava

It begins posterior to the lower edge of the right first costal cartilage, where the right and left brachiocephalic veins join, and returns to the right atrium


Brachiocephalic veins

The left and right brachiocephalic veins (or
innominate veins) are formed by the union of
internal jugular vein and subclavian vein.


The internal jugular veins are the main returning route for the venus blood of the head and neck
The subclavian veins are the main returning route for the venus blood of the upper limb
The venus blood in the thorax is drained mainly by the azygos system of veins .
We can regard the superior vena cava as the aortic arch plus the thoracic aorta for they have similar control area of our body.



Veins of head and neck

The internal jugular vein

It runs from its origin at the jugular foramen to its termination behind the sternal end of the clavicle, where it joins the subclavian vein to form the brachiocephalic vein.


VEINS OF THE FACE

a)The veins of the face accompany the arteries & drain into the common facial & retromandibular veins, they communicate with the cavernous sinus

b)The veins of each side form a W shaped arrangement, each corner of the W is prolonged upwards in to the scalp & downwards in to the neck

c)The facial vein is the largest vein of the face, begins as an angular vein at the medial angle of the eye. The angular vein continue as the facial vein running downwards and backwards joins the anterior division of the retromandibular vein to form the common facial vein, later drains into the internal jugular vein


The posterior conner of the W is formed by the join of posterior auricular vein and posterior division of the retromandibular vein. They form the external jugular vein.


Veins of thorax

THE AZYGOS VEIN

This vein drains the thoracic wall & the upper lumbar region
It forms an important channel connecting the SVC & IVC
The term azygos means unpaired
formation
The azygos vein is formed by the union of 1) ascending lumbar veins2)right subcostal vein


Tributaries of the azygos vein include:

the right superior intercostal vein (a single vessel formed by the junction of the second, third, and fourth intercostal veins),
fifth to eleventh right posterior intercostal veins,
the hemiazygos vein,
the accessory hemiazygos vein,
esophageal veins,
mediastinal veins,
pericardial veins, and
right bronchial veins


Veins of upper limb

These include the superficial veins and the deep veins. The superficial veins first drain into the deep veins and then they together return to the heart

THE SUPERFICIAL VEINS

These veins assume important in medical practice because they are most common used for IV injection & for withdrawing blood for testing

Most of the superficail veins join to form 2 large veins, cephalic & basilic


CEPHALIC VEIN

It begins from the lateral end of the dorsal venous arch
It runs upwards through

1.Roof of snuffbox
2.Winds round the distal part of the forarm
3.Runs in front of the elbow
4.Runs in the deltopectoral groove
5.Joins the axillary vein or the subclavian vein

BASILIC VEIN

It begins from the medial end of the dorsal venous arch
Runs upwards

1)along the back of the med border of the f arm

2)winds round this border near the elbow

3)it pierces the deep fascia and joins the brachial vein or axillary vein


THE MEDIAN CUBITAL VEIN

it is a large communicating vein which shunts the blood from cephalic to the basilic vein

It begins from the cephalic vein 2.5 cm below the bend of the elbow, runs obliquely upwards & medially and ends in the basilic vein

It is a ideal place for IV injection

DEEP VEINS

The deep veins accompany the arteries of the same region and bear similar names


Inferior vena cava system

This system takes charge of the drainage of the venus blood from the abdoman,pelvis and the lower limbs.

We can regard it as the abdominal aorta plus the common iliac arteries for they have similar control area of our body.



Inferior vena cava

The inferior vena cava returns blood from all structures below the diaphragm to the right atrium of the heart.

It is formed when the two common iliac veins come together at the level of vertebra LV just to the right of midline.


Tributaries to the inferior vena cava include:
the common iliac veins;
the lumbar veins;
the right testicular or ovarian vein;
the renal veins;
the right suprarenal vein;
the inferior phrenic veins;
the hepatic veins

Wednesday, April 27, 2011

Sphingolipidoses (lipid storage diseases)

These are a group of inherited diseases that are often manifested in childhood due to deficiency of sphingolipid degrading enzymes (in lysosomes) .
all are autosomal recessive disorders except Fabry disease (X-linked)

Common features:

(1) Complex lipids containing ceramide accumulate in cells, particularly neurons, causing neurodegeneration and shortening the life span.
(2) The rate of synthesis of the stored lipid is normal.
(3) The enzymatic defect is in the lysosomal degradation pathway of sphingolipids.


Monday, April 18, 2011

The Respiratory System

This consists of the lungs and the air passages that lead to and form the lungs.

The air passages branch as they enter the lungs to finally form alveoli.

This system has 3 main functions:

1.Air conduction;
2.Air filtration;
3.Gas exchange (respiration).

Also air passing through the larynx gives rise to speech and air passing over the olfactory mucosa leads to our sense of smell.



Air passages consist of a conducting portion and a respiratory portion.

The conducting portion is the air passages that lead to the sites of respiration so gas exchange can occur.

The passages external to the lungs are:
1.Nasal cavities;
2.Nasopharynx and oropharynx;
3.Larynx;
4.Trachea;
5.Paired primary bronchi.

Bronchi within the lungs branch extensively to form bronchioles, which are the terminal part of the conducting system.


The respiratory portion is the part of the tract where gas exchange takes place and includes:
Respiratory bronchioles;
Alveolar ducts;
Alveolar sacs;
Alveoli.

Capillaries within the lungs come into intimate contact with the alveoli and are the structural basis of gas exchange in the lung.

Conditioning of the air before it reaches the respiratory portion occurs and consists of warming, moistening, and removal of particulate material.


Nasal cavity

It is pyramidal in shape and it is divided in to two halves by a septum
Anterior nasal apertures
Posterior nasal apertures


Subdivisions

The nasal cavity has 3 parts
Vestibule
Olfactory Region
Respiratory region


Boundaries

Each half of nasal cavity has a
Roof
Floor
Lateral wall
Medial wall


Vestibule

Dilated part immediately inside the
anterior nasal opening. It is lined by
skin and has hairs projecting downwards called vibrissae


Olfactory region: located in upper nasal cavity, above superior nasal conchae,contains olfactory cells


Respiratory region

Lower 2/3 of nasal cavity
Thick mucous membrane due to presence of cavernous vascular tissue
its function is to warm, moisten, and clean the inspired air


Lateral wall of nasal cavity

Limen nasi – A line at the Muco cutaneous junction
Sphenoethmoidal recess-Triangular depression
Superior meatus-opening of posterior ethmoidal sinus




sphenoethmoid recess (arrow above 1)
superior concha (1)
superior meatus (tip of arrow)
middle concha (2)
middle meatus (tip of arrow)
inferior concha (3)
inferior meatus (ti of arrow)


Middle meatus

Bulla ethmoidalis- is caused by the bulging of the middle ethmoidal cells which open on or immediately above it

Hiatus semilunaris-Curved cleft below
The bulla

Infundibulum- Anterior funnel shaped expansion of hiatus



Inferior meatus

Naso lacrimal duct- opening in the anterior part of meatus


Kieselbach’s Area

Also called Little’s area, at antero-inferior part of nasal septum.
90% of nasal bleeding occurs.
Supplied by septal branch of facial artery and nasopalatine branch of spheno-palatine artery anastomose & join With Twigs of anterior ethmoidal & greater palatine arteries


1.anterior ethmoidal (ophthalmic)
2.posterior ethmoidal (opththalmic)
3.sphenopalatine (maxillary)
4.greater palatine (maxillary)
5.branch of superior labial (facial

Saturday, April 16, 2011

The Arteries


Characteristics

Symmetrical
In the trunk of the body consist of parietal and visceral branches
Shortest possible course
Run on flexor surfaces
Usually do not pass directly through muscles, avoiding compression
Together with the veins and nerves in a sheath of fascia to form neurovascular bundle

Arteries of pulmonary circulation

Pulmonary trunk Arises from right ventricle
Runs up, back ,and to the left
Bifurcates inferior to aortic arch into right and left pulmonary arteries, one for each lung


Ductus arteriosus

is a shunt connecting the pulmonary artery to the aortic arch. It allows most of the blood from the right ventricle to bypass the fetus' fluid-filled lungs
The DA begins to close when breathing is established, and is completely sealed after four to ten days to become the ligamentum arteriosum



Arteries of systemic circulation

Aorta
Ascending aorta
Aortic arch
--Brachiocephalic trunk
right common carotid a.
right subclavian a.
Left common carotid a.
Left subclavian a.

Descending aorta
Thoracic aorta
Abdominal aorta


Arteries of systemic circulation

The aorta is usually divided into 3 sections:

Ascending aorta—the section between the heart and the arch of aorta . The only branches of the ascending aorta are the right and left coronary arteries that supply the heart.

Arch of aorta— ending on the left side at level of vertebral T4/5. From right to left side at its convexity the aortic arch give off three branches for the head and upper limbs, namely the brachiocephalic trunk, left common carotid artery and the left subclavian artery.


Descending aorta—the section from the arch of aorta to the point where it divides into the common illiac arteries at level of L4

Thoracic aorta—the half of the descending aorta above the diaphram. this part of the aorta sends numerous branches to serve the thoracic wall and organs.

Abdominal aorta—the half of the descending aorta below the diaphram. It sends many branches to the abdominal wall and organs. And finally, it bifurcates into the right and left common iliac arteries in front of the L4 for the pelvis and lower limbs.


1.Arteries of the neck and head

The neck and head are supplied by the common carotid arteries and three branches from each subclavian artery.
(1)Common carotid arteries
They are the main source of the blood supply for the neck and head.
The right originates from the brachiocephalic trunk, and the left arises directly from the aortic arch .
At the upper border of the thyroid cartilage the arteries divide into the external and internal carotid arteries



1)External carotid arteries supply most tissues in the face and in the anterior area of the neck.

Superior thyroid a. - to supply upper pole of thyroid gland and larynx

Lingual a. - to supply the tongue

Facial a.

Occipital a. -- to the back of the scalp

Posterior auricular a. - supplies the skin of the back of the ear

Maxillary a. - supplies the upper and lower jaws, nasal cavity and the muscles of mastication

Superficial temporal a. - to supply the most part of the scalp

2) internal carotid arteries

Ascend and pass through the carotid canal to the skull.
They send branches to supply the brain and the eyes.
The arteries have no branches in the neck.

(2) Subclavian artery

Origin
Brachiocephalic trunk on right
Aortic arch on left
Becomes axillary artery at lateral border of first rib

Branches

Vertebral a. passes through the foramen magnum to the skull and supply the brain and the spinal cord .
Internal thoracic a.
Thyrocervical trunk
Inferior thyroid artery -supplies inferior pole of thyroid gland
Costocervical trunk



Arteries of the upper limb

1)The axillary artery
It is the continuation of the subclavian arteries at the lateral border of the first rib ,serves the large part of the upper limb, and ends at the lower border of teres major.

2)Brachial artery
The brachial artery is continuation of the axillary artery, it descends along the medial side of the humerus,divides into the radial and ulnar arteries at the level of the neck of radius.


3)Radial and Ulnar arteries

The radial artery

descends along the medial margin of the brachioradialis to the level of styloid of the radius.
it lies just lateral to the tendon of the flexor carpi radialis in diatal forarm and is easy to palpate
A superficial palmar branch enters the hand and anastomoses with the superficial palmar arch formed by the ulnar artery.


The ulnar artery

passes down the medial side of the forearm
In distal regions of the forearm ,it leaves the forearm, enters the hand by passing lateral to the pisiform bone
A major branch is the common interosseous artery, it splits immediately into the anterior and posterior interosseous arteries to supply the flexor and extensor muscle of the forearm

(4)Palmar arches

In the palm, the branches of the radial and the ulnar arteries anastomose each other to form the two arches.
The superficial palmar arch is formed by the anastomosis of the terminal part of the ulnar artery and the superficial palmar branch of the radial artery.
It gives off three common palmar digital arteries that finally split into two proper palmar digital arteries to supply the fingers.



The deep palmar arch

is formed by the anastomosis of the terminal part of the radial artery and the deep palmar branch of the ulnar artery.
The main branches of the arch include the principal thumb artery that supplies mainly the thumb and three palmar metacarpal
arteries that join to the three common palmar digital arteries.

Arteries of thorax

(1) Arteries of thoracic wall
The anterior wall of the thorax is supplied mainly by the internal thoracic artery.
It gives off the anterior intercostal arteries that anastomoses with the posterior intercostals arteries to supply the intercostals muscles.


(2) Arteries of thoracic viscera

The thoracic aorta give off the visceral branches to all the organs of the thorax except the heart.
These include the bronchial arteries to the bronchi and lung, the esophageal arteries to the esophagus, and the pericardial arteries to pericardium.
These arteries are ususlly very small and vary in their numbers and origins.





Arteries of abdomen

The abdominal aorta is the main source of blood supply of the abdomen.

It gives off 1)parietal branches to the abdominal wall and 2)visceral branches to the organs in the abdominal cavity.

1)Parietal branches

These include the inferior phrenic arteries, the lumbar arteries and the median sacral artery.
The inferior phrenic arteries supply the inferior surface of the diaphragm
The lumbar arteries supply the posterior abdominal wall
The median sacral artery supplies the sacrum and coccyx





(2)Visceral branches
They are divided into two groups: the paired branches that supply the paired abdominal organs, and the unpaired branches that serve the unpaired abdominal organs.

The paired branches of the abdominal aorta include the middle suprarenal arteries, the renal arteries, and the testicular/ovarian arteries.

The unpaired visceral branches include the celiac trunk, and the superior and inferior mesenteric arteries

1)Celiac trunk

It divides almost immediately into the left gastric, splenic and the common hepatic arteries.
These branches supply the alimantary canals from the stomach to the decending part of duodenem proximal to the great duodenal papilla.
They also supply the liver ,pancrease, gall bladder and spleen.


2)Superior mesenteric artery

It arises from the front of the aorta at the level of the L1
From its left side it sends many jejunal arteries and ileal arteries to the jejunum and ileum;
from its right side sends the ileocolic artery to the terminal part of the ileum, the cecum, the appendix and the lower part of the ascending colon; the right and middle colic arteries to the upper part of the ascending colon and the transverse colon.


3)Inferior mesenteric artery

arises from the front of the aorta at the level of L3
it gives off the left colic artery, sigmoid arteries, and superior rectal arteries.
These branches supply the the last part of the transverse colon, descending colon, sigmoid colon and the upper part of the rectum。


Arteries of pelvis and lower limb

Both of them are the branches of the common iliac arteries

The two common iliac arteries start at L4 from the end of aorta and splits into the internal and external iliac arteries in front of the sacroiliac joint.


Arteries of pelvis

Supplied by the internal iliac arteries

Main branches include:
parietal branches
a)Superior and inferior gluteal arteries -- supply the gluteal muscles
b) Obturator artery-- descends through the obturator foramen to the thigh to supply the adductor muscles



2) Visceral branches
a) Internal pudendal artery-- supply the anus, perineal muscles and external genitalia
b) Inferior rectal artery to the lower part of the rectum
c) Uterine artery supplies the uterus and vagina.

Arteries of lower limb

Supplied by the extenal iliac arteries

Femoral artery

is the continuation of the external iliac artery under the midpoint of the inguinal ligament
the largest branch is called the femoral profunda artery
It supplies the muscles of thigh
It terminates by passing through the hiatus in adductor magnus to become the popliteal artery




Popliteal artery

It is the continuation of the femoral artery, and descends through the popliteal fossa .
It gives off several branches to the knee joint and nearby muscles.
Just below the lower border of the popliteus, the popliteal artery splits into the anterior and
posteror tibial arteries.

Posterior tibial a.

is the continuation of the popliteal artery and descends downwards , branches to supply the flexor muscles of the leg.
Inferiorly, it passes behind the medial malleolus of the tibia and enters the planta. There it divides into the medial and lateral plantar arteries to serve the sole and the toes.
Another branch is the peroneal artery supplying the lateral group muscles of leg and giving a nutrient branch to the fibula.


Anterior tibial artery

pierces the interosseous membrane into the anterior surface of the leg
It then descends lateral to the tibia and sends branches to the extensor muscles of the leg.
Passing the anterior surface of the ankle joint, it becomes the dorsal pedal artery that supplies the dorsum of foot and toes.

Wednesday, April 13, 2011

Drugs of Choice for Various Seizures

1.Absence seizures (Petit Mal) in children -Ethosuximide

2.Absence seizures in Adult -Valproate

3.GTCS(Grand Mal) -Valproate

4. Atypical absence seizures -Valproate

5.Partial Seizures -CBZ

6.Myoclonic Seizures -Valproate

7.Atonic (Akinetic) Seizures -Valproate

8.Tonic Seizures -Valproate

9.Clonic Seizures -Valproate

10.Infantile spasms -Vigabatrin

11.Febrile Seizures -Diazepam (per rectal)

12.Status epilepticus -Lorazepam (i.v.)

13.Epilepsy in Pregnancy -Phenobarbitone

14.Seizures in Eclampsia -Magnesium sulphate


Drugs For Absence Seizures:

-Ethosuximide

-Sodium valproate

-Lamotrigine

-Trimethadione

-Ganaxolone

Tuesday, April 12, 2011

Anatomy of the Brain Stem




External features

Anterior view

The anterior surface of medulla oblongata is grooved by an anteromedian fissure,on either side of which are the swellings due to the pyramidal tracts. These
pyramids, in turn, are separated from the olivary eminences by the anterolateral sulcus along which the rootlets of the 12th cranial nerve emerge.
Between the olive and the inferior cerebellar peduncle there is yet another groove corresponding to the posterolateral sulcus of the spinal cord; emerging from this groove are the rootlets of cranial nerves IX, X and XI

The pons lies between the medulla and the midbrain and is connected to the cerebellum by the middle cerebellar peduncles.
Its ventral surface presents a shallow median groove and numerous transverse ridges, which are continuous laterally with the middle cerebellar peduncle.
Its junction with the medulla is marked close to the ventral midline by the emergence of the 6th
7th and 8th cranial nerves nerves.
5th cranial nerves leave the lateral part of the pons near its upper border.

The anterior surface of the midbrain is formed by the cerebral peduncles (descending cerebral pathways).

The fibres of the 3rd nerves emerge between the two cerebral peduncles in the interpeduncular fossa.


Posterior view

The posteromedian sulcus of the spinal cord is continued half-way up the medulla, where it widens out to form the posterior part of the 4th ventricle.
On either side of the fissure the posterior columns of the spinal cord expand to form two distinct tubercles, the gracile and cuneate nuclei
The dorsal surface of the pons forms the upper part of the floor of the 4th ventricle
The dorsal surface of the midbrain presents corpora quadrigeminia,including two inferior,and two superior colliculi .
The corpora quadrigemina are reflex centers involving vision and hearing





Internal structure
Cranial nerve nuclei
Non-cranial nerve nuclei
Ascending and descending pathways
Reticular formation


Cranial nerve nuclei are referred to those nuclei located in the brain stem, where the cranial nerves originate or terminate except the olfactory and optic nerve


Non-cranial nerve nuclei are referred to those nuclei which are not linked directly to any cranial nerves functionally or structurally


Ascending pathways include 1) pathways originate in the spinal cord and pass
the brain stem to higher region of the brain; 2) pathways originate in the brain
stem to higher region of the brain

Descending pathways originate in the same motor area of the cortex, but terminate in 1) spinal cord and 2) brain stem

Reticular formation is recognized as an extensive field of intermingled grey and white matter outside the fiber bundles and nuclei of the brain stem



Long ascending pathways

Passing fibrous bundles which originate in the spinal cord:

1) Medial lemniscus: fibrous bundle formed by relayed fibers from fasciculi gracilis,
cuneatus. The fibers relay in gracile and cuneate nuclei, and decussate with fibers of opposite side, finally end in the ventral posteriomedial nucleus of thalamus


2) Spinothalamic lemniscus: composed of anterior and posterior spinothalamic tracts, and terminate in the ventral posterolateral nucleus of thalamus



Long ascending pathways


Fibrous bundles originated in the brain stem:

1) Trigeminal lemniscus: formed by fibers from contralateral spinal and pontine nuclei of trigeminal n. It conducts the tactile, pressure, pain and thermal impulses to the ventral posterolateral nucleus of thalamus


2) Lateral lemniscus: formed by the fibers from the ipsilateral and controlateral cochlear nuclei; some of fibers end in the inferior colliculus, others traverse the brachium of inferior colliculus to the nucleus of medial geniculate body



Long descending pathways

Pyramidal tract : descending fiber bundles originated in motor cortex to lower motor neurons in brain stem and spinal cord, It includes 1) corticospinal tract and 2) corticonuclear tract





The cerebellum

The cerebellum is the integrative organ for the coordination and fine-tuning of movement and for the regulation of muscle tone.
it is situated in the post cr fossa behind the pons & medulla.

EXTERNAL FEATURES

The cerebellum consists of two cerebellar hemispheres that are united to each other by the median vermis.

it has 2 surfaces sup & inf.

The sup surface is convex. The two hemispheres are continued each other on this surface.

The inf surface shows a deep median notch called the vallecula which separates the rt & lft hemispheres.



Internal structure

It consists of a cortex of grey matter (in which all the afferent fibres terminate) covering a mass of white matter, in which deep nuclei of grey matter are buried.
The cerebellar cortex contains several maps of the skeletal muscles in the body
The topographic arrangement of these maps indicates that the vermis controls the axial and proximal musculature of the limbs, the intermediate part of the hemisphere controls distal musculature, and the lateral part of the hemisphere is involved in motor planning.




THE DIENCEPHALON

The diencephalon is a midline structure
which is largely embedded in the cerebrum, and therefore hidden from the surface view.

Its cavity is the 3rd ventricle the hypothalamic sulcus extending from the interventricular foramen to the cerebral aqueduct, divides each half of the diencephalon in to dorsal & ventral parts.
Further sub divisions are follows


A . Dorsal part of the diencephalon
Thalamus ( dorsal thalamus )
Metathalamus, including the med & lat geniculate bodies and
Epithalamus, including the pinial body & habenula
B . Ventral part of the diencephalon
Hypothalamus,
Subthalamus ( ventral thalamus )




THALAMUS

The thalamus serves as the major sensory
relay for the ascending tactile, visual,auditory,
and gustatory information that ultimately reaches
the cerebrum cortex.

HYPOTHALAMUS

The hypothalamus is composed of numerous
nuclei that have afferent and efferent connections
with widespread regions of the nervous system,
including the pituitary gland, the autonomic
system, and the limbic system .It takes part in the
control of many visceral & metabolic activities

META THALAMUS
It consists of medial & lateral geniculate bodies
Which are situated on either side of the midbrain, below the thalamus

Medial geniculate body

It is an oval elevation situated just below the pulvinar of the thalamus & lat to the sup colliculus
It represents the thalamic relay between the inferior colliculus (IC) and the auditory cortex (AC).

Lateral geniculate body

This is a small elevation situated anterolateral to the med geniculate body, below the thalamus.
It is the primary processing center for visual information received from the retina of the eye

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