Talk to us?

NEET MDS Synopsis - Lecture Notes
Practice Subscribe 👤 Welcome User

📖 Anatomy

Showing page 1 of 36 (142 total records)

Smooth Muscle

Anatomy

Smooth Muscle

Light microscopic Structure:

cells - long - spindle shaped,  nucleus lies in the widest widest part of the fiber,  when the fiber contract the nucleus become folded, 30 - 200 µm long,between fibres lie endomycium

Electron microscopic structure:

 Mitochondria, ribosomes, golgi, rough EPR, myofilaments are present but no sarcomeres and no Z lines,thin filaments - actin and tropomyosin (7nm), thick filaments - myosin (17nmØ)

- intermediate filaments (10 nm)

- actin and myosin overlap more than in skeletal muscle and can therefore contract more

 A rudimentary sacroplasmic reticulum is present in the form of invaginations on the surface called caveolae , So there are no T-tubules,  Cells communicate through gap junctions.

Dense bodies

Filaments are attached to dense bodies which take the place of the Z line in skeletal muscle

There are two types of dense bodies - cytoplasmic and membrane

contains a percentage actinin (like the Z line)

dense bodies transmit contractile force to adjacent fibres

 

Arrangement:

Fibres can be single or in groups, normally arranged in sheaths,  In the GIT are 2 or 3 layers

Nerve supply:

2 types:

Where it is arranged in layers a few fibres are innervated together

impulse spread through the gap junctions between fibres (slow contraction)

In the iris and the vas deferens each fiber is individually supplied (quick contraction)

FACIAL MUSCLES SPECIFIC IN EMOTIONAL EXPRESSION
Anatomy

Muscle

 

Emotion

 

Epicranius

 

Surprise

 

Orbicularisoculi

 

Squinting

 

Orbicularisoris

Pouting

Nasalis

 

Smelling

 

Zygomaticus

 

Smiling

 

Buccinator

 

Chewing

 

Mentalis

 

Doubt

 

Triangularis

 

Sadness

 

Platysma

 

Sadness

 

Masseter

 

Chewing

 

Temporalis

 

Sternness

 

Pterygoid

 

Conternation

 

Genioglossus and Styloglossus

 

Swallowing, Speaking, Chewing

 
 
The Parotid Glands
Anatomy

The Parotid Glands

  • The parotid glands are the largest of the three pairs of salivary glands.
  • Each gland is wedged between the mandible and the sternocleidomastoid muscle and partly covers them.
  • The parotid gland is wrapped with a fibrous capsule (parotid fascia) that is continuous with the deep investing fascia of the neck.
  • Viewed superficially, the parotid gland is somewhat triangular in shape.
  • Its apex is posterior to the angle of the mandible and its base is along the zygomatic arch.
  • The parotid gland overlaps the posterior part of the masseter muscle.
  • The parotid duct (Stensen's duct) is about 5 cm long and 5 mm in diameter.
  • It passes horizontally from the anterior edge of the gland.
  • At the anterior border of the masseter muscle, the parotid duct turns medially and pierces the buccinator muscle.
  • It enters the oral cavity opposite the second maxillary molar.

 

Blood Vessels of the Parotid Gland

  • This gland is supplied by branches of the external carotid artery.
  • The veins from the parotid gland drains into the retromandibular vein, which enters the internal jugular vein.

 

Lymphatic Drainage of the Parotid Gland

  • The lymph vessels of this gland end in the superficial and deep cervical lymph nodes.

 

Nerves of the Parotid Gland

  • These nerves are derived from the auriculotemporal nerve and from the sympathetic and parasympathetic systems.
  • The parasympathetic fibres are derived from the glossopharyngeal nerve (CN IX) through the otic ganglion.
  • Stimulation of these fibres produces a thin watery (serous) saliva to flow from the parotid duct.
  • The sympathetic fibres are derived from the cervical ganglia through the external carotid plexus.
  • Stimulation of these fibres produces a thick mucous saliva.
The External Nose
Anatomy

The External Nose

  • Noses vary considerably in size and shape, mainly as a result of the differences in the nasal cartilages and the depth of the glabella.
  • The inferior surface of the nose is pierced by two apertures, called the anterior nares (L. nostrils).
  • These are separated from each other by the nasal septum (septum nasi).
  • Each naris is bounded laterally by an ala (L. wing), i.e., the side of the nose.
  • The posterior nares apertures or choanae open into the nasopharynx.