Histology slides of GIT

Esophagus

1. lining epithelium is non keratinized stratified squamous epithelium
2. muscularis mucosae is unusually thick
3. inner circular and outer longitudinal muscles layers present in muscularis externa  : in upper 1/3 of esophagus it contain skeletal muscle , in middle 1/3 it contain both skeletal and smooth muscle and in lower 1/3 it contain only smooth muscle
4. outer most layer is adventitia 

Stomach

1.      lining epithelium simple columnar epithelium

2.      lamina propria contain gastric glands

3.      three smooth muscle cells layers are present in muscularis externa – inner oblique, middle circular and outer longitudinal

4.      outer serosa is present 

Duodenum

1. villi are present {projection of mucosa }
2. Submucosa contain Brunner’s glands
3. lining epithelium simple columnar epithelium
4. muscularis externa contains inner circular and outer longitudinal smooth muscles layers 

Large intestine:

1. lining epithelium simple columnar epithelium with large number of goblet
2. lamina propria contain intestinal glands
3. muscularis externa contains inner circular and outer longitudinal smooth muscles layers

 Gall bladder:

1. it is lined by simple columnar epithelium
2. epithelial diverticula or crypt (Rokitansky-Aschoff sinus)  is present
3. no submucosa
4. fibromuscular layer contain smooth muscle cells  which are randomly oriented  

Appendix:

1. Lining epithelium is simple columnar epithelium
2.  lymphatic nodules (the most characteristic property of the appendix is the presence of lymphatic nodule) are present in mucosae and submucosa
3.  3. Muscularis externa  contains inner circular and outer longitudinal smooth muscles layers
4. 4. outer serosa is present

Histology of lymphatic system

 Thymus

1.capsule of thymus  divides the thymus  into several thymic lobules

2. each thymic lobules contain outer cortex and inner medulla

3. Inner medulla  of thymic lobule contain Hassall’s corpuscles

4. outer cortex of thymic lobule contain no lymphatic nodule

SN: thymus contain only T lymphocyte

Spleen

1. White pulp is present (which is composed by central arteriole,  periarterial lymphatic

sheath & lymphatic nodule with germinal center )

2. Red pulp is present (which contain splenic cord & splenic sinusoid)

3. Capsule present

Tonsil

1.  It is lined by non-keratinized stratified squamous epithelium

2. Lymphatic nodoule with germinal center is present 

3. tonsillar crypts are present 

Lymph node

1. Sub capsular sinus is present.

2. it is divided into outer cortex and inner medulla

 3. Outer cortex   contain lymphatic nodules.

4. Capsule is present

 

Elastic artery vs medium sized artery

 Elastic artery

1. Tunica media contain numerous elastic lamina.
2. Smooth muscle cells are present in between elastic lamina
3. Tunica intima contain internal elastic lamina which is not clearly defined
4. Tunica adventitia contains collagenous connective tissue.

Medium sized artery

1. Tunica intima contain prominent internal elastic lamina
2. Tunica media contain smooth muscle cells
3. Tunica adventitia contain collagenous connective tissue

Histology of endocrine gland

 Thyroid gland

1.      Thyroid follicle is lined by simple cuboidal epithelium

2.    Thyroid follicles are filled with colloid.

3.    Thyroid follicle is formed by  Follicular cells and parafollicular cells

Adrenal gland

1. Outer cortex has three zones. zona glomerularis, zona fasciculata & zona reticularis.

2. The thichest zone is zona fasciculata contain long, parallal cords

3. Inner medulla contain several large vein (& large chromaffin

cells)

Pancreas

1. Pancreas is a mixed gland
2. Pancreatic acinus and ducts are the Exocrine components of this gland .
3. Islcts of langerhans (a tuff of cells.) are the Endocrine portion of this gland
4. Centro acinus cells are  present within lumen of the Pancreatic acinus

Internal capsule : lecture notes summary

 

Internal capsule

The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain.

1. It is a V shaped white matter (projection fibres) with its concavity directed laterally
2. It situated  between the thalamus and caudate nucleus medially and the lentiform nucleus laterally
3. Corona radiata : rostral part of projection fibres is known as corona radiata
4. Caudally it continue as crus cerebri of midbrain
5. Internal capsule contain nerve fibres which responsible for the sensory and motor inntervation of opposite half of the body

 

Parts of internal capsule

•        Anterior limb

•        Genu

•        Posterior limb

•        Retrolentiform part

•        Sublentiform part

Types of fibres present within the internal capsule

•        Motor fibres

1. Corticopontine fibres
2. Pyramidal fibres :  arises from cerebrum and relay lower motor neuron within the brain stem  and spinal cord --corticonuclear fibres and corticospinal fibres
3. Extrapyramidal fibres : arises from cerebrum and relay into  subcortical grey matter like red nucleus, corpus striatum, substantia nigra

Sensory fibres

1. Thalamocortical fibres
2. Subgroups of thalamocortical fibres
3. Anterior , superior, posterior and inferior thalamic radiation

Blood supply of internal capsule

•        The arterial supply of the internal capsule is of great clinical significance

1. Medial and lateral striate branches of middle cerebral artery :

•        SN:  lateral striate branch of middle cerebral artery is larger and frequently ruptured so  it is known as Charcot’s artery of cerebral haemorrhage :

•        it is mainly supply posterior limb of internal capsule . Posterior limb contain pyramidal and extrapyramidal fibers of upper limb, trunk and lower limb so rupture of this artery causes hemiplegia

•        Striate branches of anterior cerebral artery : it supply genu and anterior limb of internal capsule

•        Central branches of anterior choroidal artery : it supply sublentiform part of internal capsule

•        Posteriorlateral central branches of the posterior cerebral artery supply the retrolentiform and sublentiform parts of the internal capsule

 

Function: From the cerebral cortex to the brainstem, the internal capsule provides an essential conduit for the transmission of motor and sensory data. To reach the brainstem and spinal cord and regulate voluntary movements, motor fibers originating from the motor cortex pass through the internal capsule. It is also through which sensory fibers that transmit data from the thalamus to the cerebral cortex pass.

Clinical significance: Damage to the internal capsule may cause severe motor and sensory deficiencies, including hemiplegia, which is the paralysis of one side of the body, and hemianaesthesia, which is the lack of feeling on one side of the body.

Motor and sensory deficits on the opposite side of the body may result from a stroke that affects the blood supply to the internal capsule.

Development: Axons from the growing cerebral cortex reach into subcortical tissues, including the thalamus, brainstem, and spinal cord, during embryonic development, forming the internal capsule. In the central nervous system, this process is essential for creating functional connections.

Systems of Neurotransmitters: Axons within the internal capsule use a variety of neurotransmitters, including as glutamate for excitatory transmission and gamma-aminobutyric acid (GABA) for inhibitory signaling. The internal capsule and its surrounding areas are home to numerous neurotransmitter systems that are crucial for controlling neuronal activity.

Functional Organization: There is a somatotopic organization in the internal capsule, which means that distinct bodily parts are represented by different areas of the structure. For instance, compared to fibers regulating the lower limb, those delivering motor information for the upper limb are situated in different regions.

Pathology: A variety of disorders affecting the internal capsule can result in motor and sensory impairments, including multiple sclerosis, brain tumors, and traumatic brain injury, in addition to stroke.
The motor symptoms typical of neurodegenerative disorders such as Parkinson's disease and Huntington's disease can also be caused by the degradation of fibers that pass through the internal capsule.

 

 

 

how to identify lesion of nerves supply extraocular muscles of eye in an easiest way ?

 

The trochlear nerve innervation, functions of muscles and lesion

	Innervation	Function	Lesion
Extraocular muscle	Superior oblique	Intorsion (medial rotation), depression and abduction, respectively.	Trochlear nerve palsy results in upward deviation of the eye (hypertropia).

The abducent  nerve innervation, functions of muscles and lesion

	Innervation	Function	Lesion
Extraocular muscle	Lateral rectus	Abducts the eyeball.	Trochlear nerve palsy results in upward deviation of the eye (hypertropia).

Lesion of oculomotor nerve

The oculomotor nerve innervation, functions of muscles and lesion :

Lesion of this nerve make eye down and out

	Innervation	Function	Lesion
Muscle of eyelid	Levator palpebrae superioris	raises the upper eyelid	Ptosis: Drooping of the eyelid due to weakness or paralysis of the muscle responsible for elevating the upper eyelid (levator palpebrae superioris).
Extra-ocular muscle	Superior rectus muscle	eye  rotates upward	Lateral strabismus/squint: due to paralysis of medial rectus and unopposed action of lateral rectus muscle which is supply by abducens  nerve Diplopia on looking medially and superiorly.
	Medial rectus muscle	adducts the eye toward the nose
	Inferior rectus muscle	rotates the eyeball down"
	Inferior oblique	Extortion(lateral rotation) , elevation, and abduction.
Muscle of pupil	Sphincter papillae	Constriction of pupil (miosis)	Dilated pupil (mydriasis): Loss of pupillary constriction due to paralysis of the sphincter pupillae muscle, which is innervated by the oculomotor nerve.
Muscle alter curvature of lens	Ciliary  muscle	Contraction of this muscle relax suspensory ligament, so diameter of lens increase during near vision (accommodation)	Loss of accommodation: due to paralysis of medial rectus, sphincter papillae and ciliaris muscles.

Lesion of nerves supply extraocular muscle

Nerve	Lesion
Oculomotor nerve lesion	down and abducted eye
Trochlear nerve lesion	Upward and adducted eye
Abducent nerve lesion	Adducted eye

 

The oculomotor nerve innervation, functions of muscles and lesion : magic summary

 

The oculomotor nerve innervation, functions of muscles and lesion

	Innervation	Function	Lesion
Muscle of eyelid	Levator palpebrae superioris	raises the upper eyelid	Ptosis: Drooping of the eyelid due to weakness or paralysis of the muscle responsible for elevating the upper eyelid (levator palpebrae superioris).
Extra-ocular muscle	Superior rectus muscle	eye  rotates upward	Lateral strabismus/squint: due to paralysis of medial rectus and unopposed action of lateral rectus muscle which is supply by abducens  nerve Diplopia on looking medially and superiorly.
	Medial rectus muscle	adducts the eye toward the nose
	Inferior rectus muscle	rotates the eyeball down"
	Inferior oblique	Extortion, elevation, and abduction.
Muscle of pupil	Sphincter papillae	Constriction of pupil (miosis)	Dilated pupil (mydriasis): Loss of pupillary constriction due to paralysis of the sphincter pupillae muscle, which is innervated by the oculomotor nerve.
Muscle alter curvature of lens	Ciliary  muscle	Contraction of this muscle relax suspensory ligament, so diameter of lens increase during near vision (accommodation)	Loss of accommodation: due to paralysis of medial rectus, sphincter papillae and ciliaris muscles.