NEET MDS Lessons
Anatomy
Muscles of the Tongue
- The tongue is divided into halves by a medial fibrous lingual septum that lies deep to the medial groove.
- In each half of the tongue there are four extrinsic and four intrinsic muscles.
- The lingual muscles are all supplied by the hypoglossal nerve (CN XII).
- The only exception is palatoglossus, which is supplied by the pharyngeal branch of the vagus nerve, via the pharyngeal plexus.
Extrinsic Muscles of the Tongue
The Genioglossus Muscle
- This is a bulky, fan-shaped muscle that contributes to most of the bulk of the tongue.
- It arises from a short tendon from the genial tubercle (mental spine) of the mandible.
- It fans out as it enters the tongue inferiorly and its fibres attach to the entire dorsum of the tongue.
- Its most inferior fibres insert into the body of the hyoid bone.
- The genioglossus muscle depresses the tongue and its posterior part protrudes it.
The Hyoglossus Muscle
- This is a thin, quadrilateral muscle.
- It arises from the body and greater horn of the hyoid bone and passes superoanteriorly to insert into the side and inferior aspect of the tongue.
- It depresses the tongue, pulling its sides inferiorly; it also aids in retrusion of the tongue.
The Styloglossus Muscle
- This small, short muscle arises from the anterior border of the styloid process near its tip and from the stylohyoid ligament.
- It passes inferoanteriorly to insert into the side and inferior aspect of the tongue.
- The styloglossus retrudes the tongue and curls its sides to create a trough during swallowing.
The Palatopharyngeus Muscle
- Superior attachment: hard palate and palatine aponeurosis.
- Inferior attachment: lateral wall of pharynx.
- Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
- This thin, flat muscle is covered with mucous membrane to form the palatopharyngeal arch.
- It passes posteroinferiorly in this arch.
- This muscle tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly and medially during swallowing.
Intrinsic Muscles of the Tongue
The Superior Longitudinal Muscle of the Tongue
- The muscle forms a thin layer deep to the mucous membrane on the dorsum of the tongue, running from its tip to its root.
- It arises from the submucosal fibrous layer and the lingual septum and inserts mainly into the mucous membrane.
- This muscle curls the tip and sides of the tongue superiorly, making the dorsum of the tongue concave.
The Inferior Longitudinal Muscle of the Tongue
- This muscle consists of a narrow band close to the inferior surface of the tongue.
- It extends from the tip to the root of the tongue.
- Some of its fibres attach to the hyoid bone.
- This muscle curls the tip of the tongue inferiorly, making the dorsum of the tongue convex.
The Transverse Muscle of the Tongue
- This muscle lies deep to the superior longitudinal muscle.
- It arises from the fibrous lingual septum and runs lateral to its right and left margins.
- Its fibres are inserted into the submucosal fibrous tissue.
- The transverse muscle narrows and increases the height of the tongue.
The Vertical Muscle of the Tongue
- This muscle runs inferolaterally from the dorsum of the tongue.
- It flattens and broadens the tongue.
- Acting with the transverse muscle, it increases the length of the tongue.
Appendicular Skeleton
Upper extremity
• Shoulder-clavicle and scapula
Clavicle
Articulates with the manubrium at the sternal end
Articulates with the scapula at the lateral end
Slender S-shaped bone that extends horizontally across the upper part of the thorax
Scapula
Triangular bone with the base upward and the apex downward
Lateral aspect contains the glenoid cavity that articulates with the head of the humerus
Spine extends across the upper part of the posterior surface; expands laterally and
forms the acromion (forms point of shoulder)
Coracoid process projects anteriorly from the upper part of the neck of the scapula
Arm (humerus)
Consists of a shaft (diaphysis) and two ends (epiphyses)
Proximal end has a head that articulates with the glenoid fossa of the scapula
Greater and lesser tubercles lie below the head
Intertubercular groove is located between them; long tendon of the biceps attaches here
Surgical neck is located below the tubercles
o Radial groove runs obliquely on the posterior surface; radial nerve is located here
o Deltoid muscles attaches in a V-shaped area in the middle of the shaft. called the deltoid tuberosity
Distal end has two projections. the medial and lateral epicondyles
Capitulum-articulates with the radius
Trochlea-articulates with the ulqa
Forearm
Radius
Lateral bone of the forearm
Radial tuberosity is located below the head on the medial side
Distal end is broad for articulation with the wrist: has a styloid process on its lateral side
Ulna
Medial side of the forearm
Conspicuous part of the elbow joint (olecranon)
Curved surface that articulates with the trochlea of the humerus is the trochlearnotch
Lateral ide is concave (radial notch); articulates with the head of the radius Distal end contains the styloid process
Distal end contains the styloid process
Hand
Carpal bones (8)
Aranged in two rows of four
Scaphoid. lunate. triquetral. and pisiform proximal row); trapezium. trapezoid.
capitate. and hamate (distal row)
Metacarpal bones (5)
Framework of the hand
Numbered 1 to 5 beginning on the lateral side
Phalanges (14)
Fingers
Three phalanges in each finger; two phalanges in the thumb
The Cheeks
- The cheeks (L. buccae) form the lateral wall of the vestibule of the oral cavity.
- They have essentially the same structure as the lips with which they are continuous.
- The principal muscular component of the cheeks is the buccinator muscle.
- Superficial to the fascia covering this muscle is the buccal fatpad that gives cheeks their rounded contour, especially in infants.
- The lips and cheeks act as a functional unit (e.g. during sucking, blowing, eating, etc.).
- They act as an oral sphincter in pushing food from the vestibule to the oral cavity proper.
- The tongue and buccinator muscle keep the food between the molar teeth during chewing.
Sensory Nerves of the Cheeks
- These are branches of the maxillary and mandibular nerves.
- They supply the skin of the cheeks and the mucous membrane lining the cheeks.
The Meatus of the Nose
Sphenopalatine Recess
- This space is posterosuperior to the superior concha.
- The sphenoidal sinus opens into this recess.
Superior Meatus
- This is a narrow passageway between the superior and middle nasal conchae.
- The posterior ethmoidal sinuses open into it by one or more orifices.
Middle Meatus
- This is longer and wider than the superior one.
- The anterosuperior part of this meatus lead into a funnel-shaped opening, called the infundibulum, through which the frontonasal duct leads to the frontal sinus.
- There is one duct for each frontal sinus and since there may be several, there may be several frontonasal ducts.
- When the middle concha is removed, rounded elevation called the ethmoidal bulla (L. bubble), is visible
- The middle ethmoidal air cells open on the surface of the ethmoidal bulla.
- Inferior to this bulla is a semicircular groove called the hiatus semilunaris.
- The frontal sinus opens into this hiatus anterosuperiorly.
- Near the hiatus are the openings of the anterior ethmoid air cells.
- The maxillary sinus also opens into the middle meatus.
Inferior Meatus
- This is a horizontal passage, inferolateral to the inferior nasal concha.
- The nasolacrimal duct opens into the anterior part of this meatus.
- Usually, the orifice of this duct is wide and circular.
The Oral Cavity
- The oral cavity (mouth) consists of two parts: the vestibule and the mouth proper.
- The vestibule is the slit-like spaced between the cheeks and the lips and the teeth and gingivae.
- It is the entrance of the digestive tract and is also used for breathing.
- The vestibule communicates with the exterior through the orifice of the mouth.
- The oral cavity is bounded:
- Externally: by the cheeks and lips.
- Roof of oral cavity: formed by the palate.
- Posteriorly: the oral cavity communicates with the oropharynx.
The Ear
- The ear contains the vestibulocochlear organ and consists of three main parts: external, middle, and internal.
- It has two functions, balance and hearing.
- The tympanic membrane (eardrum) separates the external ear from the middle ear.
- The auditory tube joins the middle ear or tympanic cavity to the nasopharynx.
- Bones begin to form during the eighth week of embryomic life in the fibrous membranes (intramembranous ossification) and hyaline cartilage (endochondral ossification)