NEET MDS Lessons
Anatomy
Gross Features of the Tongue
- The dorsum of the tongue is divided by a V-shaped sulcus terminalis into anterior oral (presulcal) and posterior pharyngeal (postsulcal) parts.
- The apex of the V is posterior and the two limbs diverge anteriorly.
- The oral part forms about 2/3 of the tongue and the pharyngeal part forms about 1/3.
Oral Part of the Tongue
- This part is freely movable, but it is loosely attached to the floor of the mouth by the lingual frenulum.
- On each side of the frenulum is a deep lingual vein, visible as a blue line.
- It begins at the tip of the tongue and runs posteriorly.
- All the veins on one side of the tongue unite at the posterior border of the hyoglossus muscle to form the lingual vein, which joins the facial vein or the internal jugular vein.
- On the dorsum of the oral part of the tongue is a median groove.
- This groove represents the site of fusion of the distal tongue buds during embryonic development.
The Lingual Papillae and Taste Buds
- The filiform papillae (L. filum, thread) are numerous, rough, and thread-like.
- They are arranged in rows parallel to the sulcus terminalis.
- The fungiform papillae are small and mushroom-shaped.
- They usually appear are pink or red spots.
- The vallate (circumvallate) papillae are surrounded by a deep, circular trench (trough), the walls of which are studded with taste buds.
- The foliate papillae are small lateral folds of lingual mucosa that are poorly formed in humans.
- The vallate, foliate and most of the fungiform papillae contain taste receptors, which are located in the taste buds.
The Pharyngeal Part of the Tongue
- This part lies posterior to the sulcus terminalis and palatoglossal arches.
- Its mucous membrane has no papillae.
- The underlying nodules of lymphoid tissue give this part of the tongue a cobblestone appearance.
- The lymphoid nodules (lingual follicles) are collectively known as the lingual tonsil.
-> Most of the facial skeleton is formed by nine bones: four paired (nasal, zygomatic, maxilla, and palatine) and one unpaired (mandible).
-> The calvaria of the new-born infant is large compared with the relatively small fascial skeleton.
-> This results from the small size of the jaws and the almost complete absence of the maxillary and other paranasal sinuses in the new-born skull.
-> These sinuses form large spaces in the adult facial skeleton. As the teeth and sinuses develop during infancy and childhood, the facial bones enlarge.
-> The growth of the maxillae between the ages of 6 and 12 years accounts for the vertical elongation of the child’s face.
The Nasal Bones
-> These bones may be felt easily because they form the bridge of the nose.
-> The right and left nasal bones articulate with each other at the internasal suture.
-> They also articulate with the frontal bones, the maxillae, and the ethmoid bones.
-> The mobility of the anteroinferior portion of the nose, supported only by cartilages, serves as a partial protection against injure (e.g., a punch in the nose). However, a hard blow to the anterosuperior bony portion of the nose may fracture the nasal bones (broken nose).
-> Often the bones are displaced sideways and/or posteriorly.
The Maxillae
-> The skeleton of the face between the mouth and the eyes is formed by the two maxillae.
-> They surround the anterior nasal apertures and are united in the medial plane at the intermaxillary suture to form the maxilla (upper jaw).
-> This suture is also visible in the hard palate, where the palatine processes of the maxillae unite.
-> Each adult maxilla consists of: a hollow body that contains a large maxillary sinus; a zygomatic process that articulates with its mate on the other side to form most of the hard palate; and alveolar processes that form sockets for the maxillary (upper) teeth.
-> The maxillae also articulate with the vomer, lacrimal, sphenoid, and palatine bones.
-> The body of the maxilla has a nasal surface that contributes to the lateral wall of the nasal cavity; an orbital surface that forms most of the floor of the orbit; an infratemporal surface that forms the anterior wall of the infratemporal fossa; and an anterior surface that faces partly anteriorly and partly anterolaterally and is covered buy facial muscles.
-> The relatively large infraorbital foramen, which faces inferomedially, is located about 1 cm inferior to the infraorbital margin; it transmits the infraorbital nerve and vessels.
-> The incisive fossa is a shallow concavity overlying the roots of the incisor teeth, just a shallow concavity overlying the roots of the incisor teeth, just inferior to the nasal cavity. This fossa is the injection site for anaesthesia of the maxillary incisor teeth.
-> If infected maxillary teeth are removed, the bone of the alveolar processes of the maxillae begins to be reabsorbed. As a result, the maxilla becomes smaller and the shape of the face changes.
-> Owing to absorption of the alveolar processes, there is a marked reduction in the height of the lower face, which produces deep creases in the facial skin that pass posteriorly from the corners of the mouth.
The Mandible
-> This is a U-shaped bone and forms the skeleton of the lower jaw and the inferior part of the face. It is the largest and strongest facial bone.
-> The mandibular (lower) teeth project superiorly from their sockets in the alveolar processes.
-> The mandible (L. mandere, to masticate) consists of two parts: a horizontal part called the body, and two vertical oblong parts, called rami.
-> Each ramus ascends almost vertically from the posterior aspect of the body.
-> The superior part of the ramus has two processes: a posterior condylar process with a head or condyle and a neck, and a sharp anterior coronoid process.
-> The condylar process is separated from the coronoid process by the mandibular notch, which forms the concave superior border of the mandible.
-> Viewed from the superior aspect, the mandible is horseshoe-shaped, whereas each half is L-shaped when viewed laterally.
-> The rami and body meet posteriorly at the angle of the mandible.
-> Inferior to the second premolar tooth on each side of the mandible is a mental foramen (L. mentum, chin) for transmission of the mental vessels and the mental nerve.
-> In the anatomical position, the rami of the mandible are almost vertical, except in infants and in edentulous (toothless) adults.
-> On the internal aspect of the ramus, there is a large mandibular foramen.
-> It is the oblong entrance to the mandibular canal that transmits the inferior alveolar vessels and nerve to the roots of the mandibular teeth.
-> Branches of these vessels and the mental nerve emerge from the mandibular canal at the mental foramen.
-> Running inferiorly and slightly anteriorly on the internal surface of the mandible from the mandibular foramen is a small mylohyoid groove (sulcus), which indicates the course taken by the mylohyoid nerve and vessels.
-> These structures arise from the inferior alveolar nerve and vessels, just before they enter the mandibular foramen.
-> The internal surface of the mandible is divided into two areas by the mylohyoid line, which commences posterior to the third molar tooth. -> Just superior to the anterior end of the mylohyoid line are two small, sharp mental spines (genial tubercles), which serve as attachments for the genioglssus muscles.
The Zygomatic Bones
-> The prominences of the cheeks (L. mala), the anterolateral rims and much of the infraorbital margins of the orbits, are formed by the zygomatic bones (malar bones, cheekbones).
-> They articulate with the frontal, maxilla, sphenoid, and temporal bones.
-> The frontal process of the zygomatic bone passes superiorly, where it forms the lateral border of the orbit (eye socket) and articulates with the frontal bone at the lateral edge of the supraorbital margin.
-> The zygomatic bones articulate medially with the greater wings of the sphenoid bone. The site of their articulation may be observed on the lateral wall of the orbit.
-> On the anterolateral aspect of the zygomatic bone near the infraorbital margin is a small zygomaticofacial foramen for the nerve and vessels of the same name.
-> The posterior surface of the zygomatic bone near the base of its frontal process is pierced by a small zygomaticotemporal foramen for the nerve of the same name.
-> The zygomaticofacial and zygomaticotemporal nerves, leaving the orbit through the previously named foramina, enter the zygomatic bone through small zygomaticoorbital foramina that pierces it orbital surface.
-> The temporal process of the zygomatic bone unites with the zygomatic process of the temporal bone to form the zygomatic arch.
-> This arch can be easily palpated on the side of the head, posterior to the zygomatic prominence (malar eminence) at the inferior boundary of the temporal fossa (temple).
-> The zygomatic arches form one of the useful landmarks for determining the location of the pterion. These arches are especially prominent in emaciated persons.
-> A horizontal plane passing medially from the zygomatic arch separates the temporal fossa superiorly from the infratemporal fossa inferiorly.
Other Bones
There are several other, very important bones in the skull, including the palatine bone, ethmoid bone, vomer, inferior concha and the ossicles of the ear (malleus, incus and stapes). These, however, are covered to greater detail where they are relevant in the head (e.g., ethmoid bone with the orbit and nasal cavity).
The Submandibular Glands
- Each of these U-shaped salivary glands is about the size of a thumb and lies along the body of the mandible.
- It is partly superior and partly inferior to the posterior 1/2 of the base of the mandible.
- It is partly superficial and partly deep to the mylohyoid muscle.
- The submandibular duct arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscle.
- The duct passes deep and then superficial to the lingual nerve.
- It opens by one to three orifices on a small sublingual papilla beside the lingual frenulum.
- The submandibular gland is supplied by parasympathetic, secretomotor fibres from the submandibular ganglion (preganglionic fibres from the chorda tympani via the lingual nerve).
The Soft Palate
- This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
- The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
- It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).
- The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.
- During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.
- Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.
- The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
- This aponeurosis attaches to the posterior margin of the hard palate.
The Scalp
- The scalp consists of five layers of soft tissue.
- It extends from the superior nuchal line on the posterior aspect of the skull of the supraorbital margins.
- Laterally, the scalp extends into the temporal fossa to the level of the zygomatic arches.
Layers of the Scalp
- The scalp proper is composed of three fused layers. It is separated from the pericranium by loose connective tissue.
- Because of this potential areolar cleavage plane, the scalp is fairly mobile.
- Each letter of the word "S C A L P" serves as a memory key for one of the layers of the scalp: Skin, Connective Tissue, Aponeurosis Epicranialis, Loose Areolar Tissue and Pericranium.
Layer 1: Skin
- Hair covers the scalp in most people.
- The skin of the scalp is thin, especially in elderly people, except in the occipital region.
- The skin contains many sweat and sebaceous glands and hair follicles.
- The skin of the scalp has an abundant arterial supply and good venous and lymphatic drainage systems.
Layer 2: Connective Tissue
- This is a thick, subcutaneous layer of connective tissue and is richly vascularised and innervated.
- It attaches the skin to the third layer of the scalp.
- Fat is enclosed in lobules between the connective fibres.
Layer 3: Aponeurosis Epicranialis
- This is a strong membranous sheet that covers the superior aspect of the cranium.
- This aponeurosis is the membranous tendon of the fleshy bellies of the epicranius muscle.
- The epicranius muscle consists of four parts: two occipital bellies, occipitalis and two frontal bellies, frontalis that are connected by the epicranial aponeurosis.
Layer 4: Loose Areolar Tissue
- This is a subaponeurotic layer or areolar or loose connective tissue.
- It is somewhat like a sponge because it contains innumerable potential spaces that are capable of being distended by fluid.
- It is this layer that allows free movement of the scalp proper, composed of layers 1-3.
Layer 5: Pericranium
- This is a dense layer of specialised connective tissue.
- The pericranium is firmly attached to the bones by connective tissue fibres called Sharpey’s fibres, however, they can be fairly easily stripped from the cranial bones of living persons, except where they are continuous with the fibrous tissues of the cranial sutures.
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
Muscles of the larynx
Extrinsic muscles
suprahyoid: raise larynx, depress mandible for swallowing
infrahyoid: lower larynx for swallowing
both stabilize hyoid for tongue movements