NEET MDS Lessons
Anatomy
The Medial Wall of the Orbit
- This wall is paper-thin and is formed by the orbital lamina or lamina papyracea of the ethmoid bone, along with contributions from the frontal, lacrimal, and sphenoid bones (L. papyraceus, "made of papyrus" or parchment paper).
- There is a vertical lacrimal groove in the medial wall, which is formed anteriorly by the maxilla and posteriorly by the lacrimal bone.
- It forms a fossa for the lacrimal sac and the adjacent part of the nasolacrimal duct.
- Along the suture between the ethmoid and frontal bones are two small foramina; the anterior and posterior ethmoidal foramina.
- These transmit nerves and vessels of the same name.
Hip
Constitutes the pelvic girdle
United with the vertebral column
Union of three parts that is marked by a cup shaped cavity (acetabulum) Ilium
• Prominence of the hip
• Superior border is the crest
• Anterosuperior spine-projection at the anterior tip of the crest
• Corresponding projections on the posterior part are the posterosuperior and posteroinferior iliac spines
• Greater sciatic notch-located beneath the posterior part
• Most is a smooth concavity (iliac fossa)
• Posteriorly it is rough and articulates with the sacrum in the formation of the sacroiliac joint
Pubic bone
Anterior part of the innominate bone
Symphysis pubic-joining of the two pubic bones at the midline
Body and two rami
• Body forms one fifth of the acetabulum
• Superior ramis extends from the body to the median plane: superior border forms the pubic crest
• Inferior ramus extends downward and meets with the ischium
• Pubic arch is formed by the inferior rami of both pubic hones
Ischium
Forms the lower and back part of the innominate bone
Body
• Forms two fifths of the accrabulum
• Ischial tuberosiry-supports the body in a sitting position
• Ramus-passes upward to join the inferior ramus of rhe pubis; known as rhe obturator foramen
Pelvis
Fanned by the right and left hip bones, sacrum, and coccyx
Greater pelvis
o Bounded by the ilia and lower lumbar vertebrae
o Gives support to the abdominal viscera
Lesser pelvis
o Brim of the pelvis corresponds to the sacral promontory
o Inferior outlet is bounded by the tip of the coccyx, ischial tuberosities, and inferior rami of the pubic bones
Female pelvis
o Shows adaptations related to functions as a birth canal Wide outlet
o Angle of the pubic arch is obtuse
Male pelvis
o Shows adaptations that contribute to power and speed
o Heart-shaped outlet
o Angle of the pubic arch is acute
Thigh
Femur-longest and strongest bone of the body
Proximal end has a rounded head that articulates with the acetabulum
Constricted portion-the neck
Greater and lesser trochanters
Slightly arched shaft; is concave posteriorly
o Linea aspera-strengthened by this prominent ridge
o Site of attachment for several muscles
Distal end has two condyles separated on the posterior side by the intercondyloid notch
Knee cap
Patella-sesamoid bone
Embedded in the tendon of the quadriceps muscle
Articulates with the femur
Leg
Tibia-medial bone
o Proximal end has two condyles that articulate with the femur
o Triangular shaft
Anterior-shin
Posterior-soleal line
Distal-medial malleolus that articulates with the latus to form the ankle joint
Fibula-lateral bone
o Articulates with the lateral condyle of the tibia but does not enter the knee joint
o Distal end projects as the lateral malleolus
Ankle, foot, and toes
Adapted for supporting weight but similar in structure to the hand
Talus
o Occupies the uppennost and central position in the tarsus
o Distributes the body weight from the tibia above to the other tarsal bones
Calcaneus (heel)-Iocated beneath the talus
Navicular-located in front of the talus on the medial side; articulates with three cuneifonn bones distally
Cuboid-lies along the lateral border of the navicular bone
Metatarsals
o First, second, and third p1etatarsals lie in front of the three cuneifonn bones
o (2) Fourth and fifth metatarsals lie in front of the cuboid bone
Phalanges
o Distal to the metatarsals
o (2) Two in the great toe; three in each of the other four toes .
Longitudinal arches in the foot (2)
o Lateral-fonned by the calcaneus, talus, cuboid, and fourth and fifth metatarsal bones
o Medial-fonned by the calcaneus, talus, navicular, cuneifonn, and first, second, and third metatarsal bones
Transverse arches-formed by the tarsal and metatarsal bones
Innervation of the Skin
- Innervation of the skin is mainly through the three branches of the trigeminal nerve (CN V).
- Some skin over the angle of the mandible and anterior and posterior of the auricle is supplied by the great auricular nerve from the cervical plexus.
- Some cutaneous branches of the auricular branch of the facial nerve also supplies skin on both sides of the auricle.
- The trigeminal nerve is the general sensory nerve to the head, particularly the face, and is the motor nerve to the muscles of mastication.
The Ophthalmic Nerve
- This is the superior division of the trigeminal nerve, the smallest of the three branches and is wholly sensory.
- The ophthalmic nerve divides into three branches: the nasociliary, frontal and lacrimal just before entering the orbit through the superior orbital fissure.
- The nasociliary nerve supplies the tip of the nose through the external nasal branch of the anterior ethmoidal nerve.
- The frontal nerve is the direct continuation of CN V1 and divides into two branches, the supraorbital and supratrochlear.
- The supratrochlear nerve supplies the middle part of the forehead.
- The supraorbital nerve supplies the lateral part and the front of the scalp.
- The lacrimal nerve, the smallest of the main ophthalmic branches, emerges over the superolateral orbital margin to supply the lacrimal gland and the lateral part of the upper eyelid.
The Maxillary Nerve
- This is the intermediate division of the trigeminal nerve.
- It has three cutaneous branches.
- The infraorbital nerve is the largest terminal branch of the maxillary nerve.
- It passes through the infraorbital foramen and breaks up into branches that supplies the skin on the lateral aspect of the nose, upper lip and lower eyelid.
- The zygomaticofacial nerve, a small branch of the maxillary, emerges from the zygomatic bone from a foramen with the same name.
- It supplies the skin over the zygomatic bone.
- The zygomaticotemporal nerve emerges from the zygomatic bone from foramen of the same name.
- It supplies the skin over the temporal region.
The Mandibular Nerve
- This is the inferior division of the trigeminal nerve.
- Of the three division of the trigeminal nerve, CN V3 is the only one that carries motor fibres (to the muscles of mastication).
- The main sensory branches of the mandibular nerve are the buccal, auriculotemporal, inferior alveolar and lingual nerves.
- The buccal nerve is a small branch of the mandibular that emerges from deep to the ramus of the mandible.
- It supplies the skin of the cheek over the buccinator muscle, the mucous membrane lining the cheek, and the buccal surface of the gingiva.
- The auriculotemporal nerve passes medially to the neck of the mandible and then turns superiorly, posterior to its head and anterior to the auricle. It then crosses over the root of the zygomatic process of the temporal bone, deep to the superficial temporal artery.
- It supplies the auricle, external acoustic meatus, tympanic membrane, and the skin in the temporal region.
- The inferior alveolar nerve is the large terminal branch of the posterior division of the mandibular nerve (the lingual nerve is the other terminal branch).
- It enters the mandible through the mandibular foramen to the mandibular canal. In the canal, it gives branches to the mandibular teeth.
- Opposite the mental foramen, this nerve divides into the mental nerve and the incisive nerve.
- The incisive nerve supplies the incisor teeth, the adjacent gingiva and the mucosa of the lower lip.
- The mental nerve emerges from the mental foramen and supplies the skin of the chin and the skin and mucous membrane of the lower lip and gingiva.
- The lingual nerve is the smaller terminal branch of the mandibular nerve.
- It supplies the general sensory fibres to the anterior two-thirds of the tongue, the floor of the mouth and the gingivae of the mandibular teeth.
The Tongue
- The tongue (L. lingua; G. glossa) is a highly mobile muscular organ that can vary greatly in shape.
- It consists of three parts, a root, body, and tip.
- The tongue is concerned with mastication, taste, deglutition (swallowing), articulation (speech), and oral cleansing.
- Its main functions are squeezing food into the pharynx when swallowing, and forming words during speech.
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.
Nerves of the Palate
- The sensory nerves of the palate, which are branches of the pterygopalatine ganglion, are the greater and lesser palatine nerves.
- They accompany the arteries through the greater and lesser palatine foramina, respectively.
- The greater palatine nerve supplies the gingivae, mucous membrane, and glands of the hard palate.
- The lesser palatine nerve supplies the soft palate.
- Another branch of the pterygopalatine ganglion, the nasopalatine nerve, emerges from the incisive foramen and supplies the mucous membrane of the anterior part of the hard palate.
Vessels of the Palate
- The palate has a rich blood supply from branches of the maxillary artery.
Movements of the Temporomandibular Joint
- The two movements that occur at this joint are anterior gliding and a hinge-like rotation.
- When the mandible is depressed during opening of the mouth, the head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the articular tubercle.
- As this anterior gliding occurs, the head of the mandible rotates on the inferior surface of the articular disc.
- This permits simple chewing or grinding movements over a small range.
- Movements that are seen in this joint are: depression, elevation, protrusion, retraction and grinding
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