NEET MDS Lessons
Anatomy
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
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First pouch |
Auditory tube, which comes in contact with epithelial line of first pharyngeal cleft, where future external acoustic meatus will form. Distal portion will form tympanic cavity (lining will become eardrum) Proximal portion will become auditory tube |
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Second pouch |
Forms buds that penetrate surrounding mesenchyme, which together form the palatine tonsils |
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Third pouch |
Forms thymus and inferior parathyroid glands |
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Fourth pouch |
Forms superior parathyroid glands |
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Fifth pouch |
Forms utlimobranchial body |
The Auditory Ossicles
The Malleus
- Its superior part, the head, lies in the epitympanic recess.
- The head articulates with the incus.
- The neck, lies against the flaccid part of the tympanic membrane.
- The chorda tympani nerve crosses the medial surface of the neck of the malleus.
- The handle of the malleus (L. hammer) is embedded in the tympanic membrane and moves with it.
- The tendon of the tensor tympani muscle inserts into the handle.
The Incus
- Its large body lies in the epitympanic recess where it articulates with the head of the malleus.
- The long process of the incus (L. an anvil) articulates with the stapes.
- The short process is connected by a ligament to the posterior wall of the tympanic cavity.
The Stapes
- The base (footplate) of the stapes (L. a stirrup), the smallest ossicle, fits into the fenestra vestibuli or oval window on the medial wall of the tympanic cavity.
Functions of the Auditory Ossicles
- The auditory ossicles increase the force but decrease the amplitude of the vibrations transmitted from the tympanic membrane.
Genioglossus Muscle
- Origin: Mental spine of the mandible.
- Insertion: Dorsum of the tongue and hyoid bone.
- Nerve Supply: Hypoglossal nerve (CN XII).
- Arterial Supply: Sublingual and submental arteries.
- Action: Depresses and protrudes the tongue.
The Lips
- These are mobile muscular folds that surround the mouth, the entrance of the oral cavity.
- The lips (L. labia) are covered externally by skin and internally by mucous membrane.
- In between these are layers of muscles, especially the orbicularis oris muscle.
- The upper and lower lips are attached to the gingivae in the median plane by raised folds of mucous membrane, called the labial frenula.
Sensory Nerves of the Lips
- The sensory nerves of the upper and lower lips are from the infraorbital and mental nerves, which are branches of the maxillary (CN V2) and mandibular (CN V3) nerves.
The External Ear
- The auricle (L. auris, ear) is the visible, shell-like part of the external ear.
- It consists of a single elastic cartilage that is covered on both surfaces with thin, hairy skin.
- The external ear contains hairs, sweat glands, and sebaceous glands.
- The cartilage is irregularly ridged and hollowed, which gives the auricle its shell-like form.
- It also shapes the orifice of the external acoustic meatus.
The Ear Lobule
- The ear lobule (earlobe) consists of fibrous tissue, fat and blood vessels that are covered with skin.
- The arteries are derived mainly from the posterior auricular artery and the superficial temporal artery.
- The skin of the auricle is supplied by the great auricular and auriculotemporal nerves.
- The great auricular nerve supplies the superior surface and the lateral surface inferior to the external acoustic meatus with nerve fibres from C2.
- The auriculotemporal nerve supplies the skin of the auricle superior to the external acoustic meatus.
The External Acoustic Meatus
- This passage extends from the concha (L. shell) of the auricle to the tympanic membrane (L. tympanum, tambourine). It is about 2.5 cm long in adults.
- The lateral 1/3 of the S-shaped canal is cartilaginous, whereas its medial 2/3 is bony.
- The lateral third of the meatus is lined with the skin of the auricle and contains hair follicles, sebaceous glands, and ceruminous glands.
- The latter glands produce cerumen (L. cera, wax).
- The medial two-thirds of the meatus is lined with very thin skin that is continuous with the external layer of the tympanic membrane.
- The lateral end of the meatus is the widest part. It has the diameter about that of a pencil.
- The meatus becomes narrow at its medial end, about 4 mm from the tympanic membrane.
- The constricted bony part is called the isthmus.
- Innervation of the external acoustic meatus is derived from three cranial nerves:
- The auricular branch of the auriculotemporal nerve (derived from the mandibular, CN V3).
- The facial nerve (CN VII) by the branches from the tympanic plexus.
- The auricular branch of the vagus nerve (CN X).
The Tympanic Membrane
- This is a thin, semi-transparent, oval membrane at the medial end of the external acoustic meatus.
- It forms a partition between the external and middle ears.
- The tympanic membrane is a thin fibrous membrane, that is covered with very thin skin externally and mucous membrane internally.
- The tympanic membrane shows a concavity toward the meatus with a central depression, the umbo, which is formed by the end of the handle of the malleus.
- From the umbo, a bright area referred to as the cone of light, radiates anteroinferiorly.
- The external surface of the tympanic membrane is supplied by the auriculotemporal nerve.
- Some innervation is supplied by a small auricular branch of the vagus nerve (CN X); this nerve may also contain some glossopharyngeal and facial nerve fibres.
The Sublingual Glands
- These are the smallest of the three paired salivary glands and the most deeply situated.
- They are almond-shaped and lie in the floor of the mouth between the mandible and the genioglossus muscle.
- The paired glands unite to form a horseshoe-shaped glandular mass around the lingual frenulum.
- Numerous small ducts (10 to 12) open into the floor of the mouth.
- Sometimes one of the ducts opens into the submandibular duct.
- The nerves the accompany the submandibular and sublingual glands are derived from the lingual and chorda tympani nerves and from the sympathetic nerves.
- The parasympathetic secretomotor fibres are from the submandibular ganglion.