NEET MDS Lessons
Anatomy
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Ossification
- Intramembranous-found in the flat bones of the face
- Mesenchymal cells cluster and form strands
- Strands are cemented in a uniform network. Which is known as osteoid
- Calcium salts are deposited; osteoid is converted to bone
- Trabeculae are formed and make cancellous bone with open spaces known as marrow cavities
- Periosteum forms on the inner and outer surfaces of the ossification centers
- Surface bone becomes compact bone
- Endochondral-primary type of ossification In the human
Classified on functional Basis
Secretion ,Protection and waterproofing, Absorbtion, Transport, Sensory
Secretion
Glandular epithelium’s 3 types:
- Exocrine - with ducts
- endocrine - without ducts
- mixed exo-endocrine
Exocrine glands: One cell
- goblet cells
- In lining epitheliums of respiratory tract and GIT
- Secretes musin (protein) Musin + water = mucus, Mucus is a lubricant
More than one cell
Simple: Has a single duct,
- Acinar - mucus glands of the penile urethra
- Tubular - cripts of Lieberkuhn
- Coiled tubular - sweat gland
- Spiral tubular - Gland of Moll
- Branched tubular - mucous glands of the pyloric region
- Branched acinar - sebaceous gland in the skin
Compound
- Consists of a branched duct with numerous secretory end organs
- Compound tubular - Brünners glands
- Compound alveolar - mammary, prostate, pancreas, parotid
- Compound tubuloalveolar - submandibular-, sublingual salivary glands
Endocrine glands
Secrete directly into the blood
One cell : mast cells, in soft CT, near capillaries,
secrete - heparin - histamine
More than one cell
Cells can be arranged in the following ways:
- Cords - adrenal glands, parathyroid, anterior pituitary
- anastomosing cords with dilated blood capillaries in-between
- Isles - pancreas
- Follicles - thyroid
- cells line a follicle filled with non-cellular material
The Arteries of the Face
- The superficial arteries are derived from the external carotid arteries.
The Facial Artery
- This is the chief artery of the face.
- It arises from the external carotid artery and winds its way to the inferior border of the mandible, just anterior to the masseter muscle.
- It hooks around the inferior border of the mandible and grooves the bone. Here the artery is superficial, just beneath the platysma and its pulsation can be felt.
- In its course over the face to the medial angle of the eye, the facial artery crosses the mandible, buccinator muscle, and maxilla.
- It lies deep to the zygomaticus major.
- The facial artery ends by sending branches to the lip and side of the nose.
- The part of the artery that runs along the side of the nose to supply the eyelids is called the angular artery.
The Superficial Temporal Artery
- This artery is the smaller of the two terminal branches of the external carotid artery (the other is the maxillary artery).
- It begins deep to the parotid gland, posterior to the neck of the mandible, and ascends superficial to the posterior end of the zygomatic process of the temporal bone. It then enters the temporal fossa.
- The superficial temporal artery ends in the scalp by dividing into the frontal and parietal branches.
- Pulsation of this artery can be felt by compressing the root of the zygomatic process of the temporal bone.
The Transverse Facial Artery
- This small artery arises from the superficial temporal artery before it emerges from the parotid gland.
- It crosses the face superficial to the masseter muscle, about a fingerbreadth inferior to the zygomatic arch.
- It divides into numerous branches that supply the parotid gland and duct, the masseter muscle, and the skin of the face.
- It anastomoses with branches of the facial artery.
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Pharyngeal Arch |
Arch Artery |
Cranial Nerve |
Skeletal elements |
Muscles |
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1 |
Terminal Branch of maxillary artery |
Maxillary and mandibular division of trigemenial (V) |
Derived from arch cartilages (originating from neural crest): From maxillary cartilages: Alispenoid, incus From mandibular: Mackel’s cartilage, malleus
Upper portion of external ear (auricle) is derived from dorsal aspect of 1st pharyngeal arch.
Derived by direct ossification from arch dermal mesenchyme: Maxilla, zygomatic, squamous portion of temporal bone, mandible
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Muscles of mastication (temporalis, masseter, and pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini (originate from cranial somitomere 4) |
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2 |
Stapedius artery (embryologic) and cortiotympanic artery (adult) |
Facial nerve (VII) |
Stapes, styloid process, stylohyoid ligament, lesser horns and upper rim of hyoid (derived from the second arch cartilage; originate from neural crest).
Lower portion of external ear (auricle) is derived from 2nd pharyngeal arch. |
Muscles of facial expression (orbicularis oculi, orbicularis oris, auricularis, platysma, fronto-ooccipitalis, buccinator), posterior belly of digastric, stylohyoid, stapedius (originate from cranial somitomere 6) |
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3 |
Common carotid artery, most of internal carotid |
Glossopharyngeal (IX) |
Lower rim and greater horn of hyoid (derived from the third arch cartilage; originate from neural crest cells) |
Sytlopharyngeus (originate from cranial somitomere 7) |
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4 |
Left: Arch of aorta; Right: Right subclavian artery; Original sprouts of pulmonary arteries |
Superior laryngeal branch of vagus (X) |
Laryngeal cartilages (Derived from the 4th arch cartilage, originate from lateral plate mesoderm) |
Constrictors of pharynx, cricothyroid, levator veli palatine (originate from occipital somites 2-4) |
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6 |
Ductus arteriosus; roots of definitive pulmonary arteries |
Recurrent laryngeal branch of vagus (X) |
Laryngeal cartilages (derived from the 6th-arch cartilage; originate from lateral plate mesoderm) |
Intrinsic muscles of larynx (originate from occipital somites 1 and 2) |
Muscles of the Pharynx
- This consists of three constrictor muscles and three muscles that descend from the styloid process, the cartilaginous part of the auditory tube and the soft palate.
External Muscles of the Pharynx
- The paired superior, middle, and inferior constrictor muscles form the external circular part of the muscular layer of the wall.
- These muscles overlap each other and are arranged so that the superior one is innermost and the inferior one is outermost.
- These muscles contract involuntarily in a way that results in contraction taking place sequentially from the superior to inferior end of the pharynx.
- This action propels food into the oesophagus.
- All three constrictors of the pharynx are supplied by the pharyngeal plexus of nerves, which lies on the lateral wall of the pharynx, mainly on the middle constrictor of the pharynx.
- This plexus is formed by pharyngeal branches of the glossopharyngeal (CN IX) and vagus (CN X) nerves.
The Superior Constrictor Muscle
- Origin: pterygoid hamulus, pterygomandibular raphe, posterior end of the mylohyoid line of the mandible, and side of tongue.
- Insertion: median raphe of pharynx and pharyngeal tubercle.
- Innervation: though the pharyngeal plexus of nerves.
- The pterygomandibular raphe is the fibrous line of junction between the buccinator and superior constrictor muscles.
The Middle Constrictor Muscle
- Origin: stylohyoid ligament and greater and lesser horns of hyoid bone.
- Insertion: median raphe of pharynx.
- Innervation: through the pharyngeal plexus of nerves.
The Inferior Constrictor Muscle
- Origin: oblique line of thyroid cartilage and side of cricoid cartilage.
- Insertion: median raphe of pharynx.
- Innervation: through the pharyngeal plexus of nerves.
- The fibres arising from the cricoid cartilage are believed to act as a sphincter, preventing air from entering the oesophagus.
Gaps in the Pharyngeal Musculature
- The overlapping arrangement of the three constrictor muscles leaves 4 deficiencies or gaps in the pharyngeal musculature.
- Various structures enter and leave the pharynx through these gaps.
- Superior to the superior constrictor muscle, the levator veli palatini muscle, the auditory tube, and the ascending palatine artery pass through a gap between the superior constrictor muscle and the skull.
- Superior to the superior border of the superior constrictor, the pharyngobasilar fascia blends with the buccopharyngeal fascia to form, with the mucous membrane, the thin wall of the pharyngeal recess.
- Between the superior and middle constrictor muscles, the gateway to the mouth, though which pass the stylopharyngeus muscle, the glossopharyngeal nerve (CN IX), and the stylohyoid ligament.
- Between the middle and inferior constrictor muscles, the internal laryngeal nerve and the superior laryngeal artery and vein pass to the larynx.
- Inferior to the inferior constrictor muscles, the recurrent laryngeal nerve and inferior laryngeal artery pass superiorly into the larynx.
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Mesodermal Origin |
Muscles |
Innervation |
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Somitomeres 1, 2 |
Superior, medial and ventral recti |
Oculomotor (III) |
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Somitomere 3 |
Superior oblique |
Trochlear (IV) |
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Somitomere 4 |
Jaw-closing muscles |
Trigeminal (V) |
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Somitomere 5 |
Lateral rectus |
Abducens (VI) |
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Somitomere 6 |
Jaw-opening and other 2nd arch muscles |
Facial (VII) |
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Somitomere 7 |
Stylopharyngeus |
Glossopharyngeal (IX) |
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Somites 1, 2 |
Intrinsic laryngeals |
Vagus (X) |
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Somites 2-5 |
Tongue muscles |
Hypoglossal (XII) |
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