Functional anatomy of the skull & muscles of the head. Dr. Oksana Ivanivna Petrichko Department of Human Anatomy and Histologi

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1 Functional anatomy of the skull & muscles of the head Dr. Oksana Ivanivna Petrichko Department of Human Anatomy and Histologi

2 Plan of the lecture Development of the muscles of the head Morphofunctional characteristics of the muscles of the head Fasciae of the head muscles Topography of the head Biomechanics of the temporomandibular joint

3 Development of the muscles of the head & neck The main part of the muscles of the head and neck have brachiometric origin Sternohyoideus m., Sternothyreoideus m., Thyreohyoideus m., Omohyoideus m., Geniohyoideus m., Scalenic mm., Prevertebral mm.

4 General characteristics of the muscles of the head & neck Muscles of the head and some muscles of the neck are derivatives of the bronchial arches. Often they are included in category of the visceral muscles. Their function serves like criterion. These muscles are voluntary, at superior vertebrates they provide for: 1- mastication, 2- deglutition, 3- respiration, 4- phonation, 5- partially hearing, 6- articulate speech.

5 Groups of the facial expression muscles: I epicranial m. II- surrounding ear III- surrounding eye IV surrounding nose V- surrounding mouth

6 Muscles of facial expression: Associated with (1) the forehead, (2) orbit, (3) mouth, and (4) nose.

7 Deep fascia exists in the regions of the parotid glands and the masseter muscles. It forms capsules around these structures. The other regions of the face have much subcutaneous tissue, but no deep fascia.

8 Characteristics of the muscles of facial expression They have bony origin. They are inserted into the skin /without the tendons/. They arrange themselves around the openings of the face as 2 groups: sphincter group & dilator group. They intermingle with each other. They are supplied by the facial nerve. Fascia covers the parotid gland and buccinator muscle only.

9 18 paired muscles participate in facial expression Major muscles involved in clinical assessment Frontalis Orbicularis oculi Zygomaticus major Orbicularis oris Lip depressors Functional elements Nasolabial fold (NLF) Smile dynamics

10 Galea aponeurotica It is interposed between the frontalis and occipitalis portions of the occipitofrontalis muscle. These muscles place the aponeurosis under tension so that deep transverse lacerations of the scalp gape widely.

11 Buccal fat pat & Buccinator muscle

12 Buccal fat pad Before After Buccal pad reduction

13 End

14 3 basic smile patterns Zygomaticus major smile Most common type (67%) Dominated by zygomaticus major and buccinator muscle Corners of the mouth elevate first Canine smile 2nd most common (31%) Mainly controlled by levator labii superioris contracting prior to zygomaticus major and buccinator Dominant upward elevation of lip followed by elevation of corners of the mouth Full-denture smile Least common (2%) Due to contraction of elevator and depressors of the lips and angles of the mouth Maxillary and mandibular teeth displayed

15 Full Denture Smile: 3% Canine Smile: 31% Zygomaticus major smile: 66%

16 Muscles of mastication Arise from the temporal & infratemporal fossae Are inserted to the mandible Are supplied by mandibular nerve All of them elevate the mandible except the lateral pterygoid which lowers it by pulling forward on condylar process All of them protrude the mandible except Temporal m. which retracts it The pterygoid mm. move the mandible from side to side

17 Masticatory muscles Masseter Origin - inferior border and medial surface of zygomatic arch Insertion - lateral surface of ramus of mandible and angle of mandible Action: elevates mandible Temporalis Origin: temporal fossa Insertion: coronoid process of mandible Action: elevates and retracts mandible Lateral pterygoid Medial pterygoid

18 MASTICATION MUSCLES

19 True Muscles of mastication Accessory Muscles of mastication ADDUCTORS jaw closing/raising All V3 innervation 1. Temporalis m. 2. Masseter m. 3. Medial pterygoid 4. Lateral pterygoid upper head: to articular disc lower head: to neck of mandibular condyle Vital for normal chewing, but not mandibular adductors/protractors Buccinator VII Digastric V3 & VII Tongue XII

20 Fasciae of the head *Muscles of the facial expression don t have the fascia, except the buccinator muscle which is covered posteriorly with the thick buccopharyngeal fascia - it blends with the fatty tissue of the cheek (anteriorly) - it fuses with the pterigomandibular raphe (posteriorly) - is continuous with the connective tissue covering of the pharyngeal muscles *Muscles of the mastication possess of the fasciae: 1) Temporal fascia (fascia temporalis) -arises above from the temporal line -covers the temporal muscle 2) Masseteric fascia (fascia masseterica) = Parotideomasseteric Fascia - is a strong layer of fascia derived from the deep cervical fascia on the human head and neck. It covers the Masseter, and is firmly connected to it. Above, this fascia is attached to the lower border of the zygomatic arch, and behind, it invests the parotid gland. -arises above from the zygomatic arch -invests the lateral surface of the masseter muscle -attaches to the mandibular border (below) the mandibular branch (anteriorly+posteriorly) -is connected with the parotid fascia (fascia parotidea) which covers the salivary

21 Fascia of the Face Superficial fascia is copious and loose however, there is no discrete layer of deep fascia of the face except

22 Capsule of the parotid gland The parotid gland is enclosed within a welldefined capsule which extension of the investing fascia of the neck. The superficial capsule is thick and unyielding and tightly affixed to the underlying glandular tissue by numerous fibrous septa. The deep capsule id quite thin and easily disrupted.

23 Parallel to the carotid sheath and along its medial aspect the prevertebral fascia gives off a thin lamina, the buccopharyngeal fascia, which closely invests the constrictor muscles of the pha rynx and is continued forward from the constrictor pharyngis superior onto the buccinator. It is attached to the prevertebral layer by loose connective tissue only, and thus an easily distended space, the retropharyngeal space, is found between them.

24 1) Temporal fascia (fascia temporalis) *arises above from the temporal line *covers the temporal muscle *below the temporal line it attaches to the zygomatic arch and separates into 2 layers: 1. superficial / fuses with the external surface of the zygomatic arch / 2. deep / fuses with the internal surface of the zygomatic arch / Between them the interfascial space is formed /is filled with fatty tissue/

25 Temporal fascia

26 Topography of the head The soft tissue envelope of the cranial vault is called the scalp. The scalp extends from the external occipital protuberance and superior nuchal lines to the supraorbital margins. The scalp consists of 5 layers: - the skin, - connective tissue, - epicranial aponeurosis, - loose areolar tissue, - pericranium. Coronal section of skull, scalp & meninges The first 3 layers are bound together as a single unit. This single unit can move along the loose areolar tissue over the pericranium, which is adherent to the calvarium.

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28 Topography of the head I. Spaces of the skull cap a) subaponeurotic between the epicranian aponeurosis and periostium of the skull cap bones. Contents: loose connective tissue. The loose areolar tissue provides a potential subaponeurotic space that allows fluids and blood to pass from the scalp to the upper eyelids. Subgaleal (subaponeurotic) haemorrhage is a serious. Neonatal caregivers should be able to recognize the occurrence of this type of bleeding and to institute appropriate forms of management. b) subperiostal between the periosteum & external plate of the skull cap bones. It is placed at the limits of each cranial bone because the periosteum of the region of the skull sutures is fused with the bones. Along the suture lines, the pericranium becomes continuous with the endosteum. A subperiosteal hematoma, therefore, forms in the shape of the skull bones.

29 The skin has the greatest concentration of hair and sebaceous glands The superficial fascia is dense connective tissue that binds the skin strongly to the underlying galea aponeurotica The vasculature of the scalp runs primarily in it. lt is rich and widely anastomnotic Wounds of the scalp bleed profusely but heal well.

30 Subaponeurotic space (loose connective tissue) Extracranial hematoma, the result of bleeding in the subaponeurotic space, can extend over the cranium. lt can extend posteriorly, to the superior nuchal line; anteriorly, into the eyelids to produce the black eye ; and lateraliy, to the temporal line. The loose connective tissue layer provides the plane of separation of the scalp from the calvaria or for the surgeon elevating the scalp from the periosteum. Contains a rich network of deep arteries and veins. Therefore, this layer has been called the dangerous area. Infarction may spread to the substance of the bones, to venous channels within the cranial cavity, or to the brain.

31 Topography of the head II. Spaces of the temporal region a) interaponeurotic between the superficial & deep laminae of the temporal fascia which covers the temporal muscle. Contents: ţesutul adipos prin care trece artera şi vena temporală medie. b) subaponeurotic between the fascia & şi temporal muscle. Contents: a part of the fat body of the cheek & vein of the m.temporal muscle. c) deep temporal between the deep fascicles of the temporal muscle & periosteum. Downward this space is open, it is continuous with the temporo-pterygoid & suprapterygoid. Contents: deep temporal blood vessels and nerves.

32 The Temporal space is divided into two compartments by the temporalis muscle. The deep temporal space is the potential space that lie between the lateral surface of the skull and medial surface of the temporalis muscle. Whereas the superficial temporal space lies between the temporalis muscle and its overlying fascia. The deep and superficial temporal spaces are involved indirectly as a result of an infection spreading superiorly from the inferior pterygomandibular and submasseteric spaces, respectively.

33 Topography of the head III. Spaces of the lateral part of the face a) Space of the parotid gland Contents: parotid gland, facial & auriculotemporal nerves, external carotid artery with its branches, retromandibular vein & parotid lymph nodes.

34 b) temporopterygoid between the lateral pterygoid & the temporal muscles. Contents: maxillary artery & the pterygoid venous plexus. Upward this space is continuous with the deep temporal space.

35 Masseter space c) masseteromandibular between the maseter m. & the branch of the mandible. Contents: connective tissue whith the neurovascular fascicle of the maseter muscle. Upward this space communicates with the temporopterygoid space under the zigomatic arch. mandible

36 Interpterygoid space d) interpterygoid between the lateral & medial pterygoid the temporal muscles Contents: inferior alveolar nerve with its branches, inferior alveolar artery & deep part of the pterigoid venous plexus.

37 e) Suprapterygoid space It lies between the superior head of the lateral pterygoid m. & infratemporală surface of the greater wing of the sphenoid bone. Contents: masseteric & deep temporal arteries & nerves. Communicates with the spaces : interpterygoid, temporo pterigoid & deep temporal.

38 f) Pterygomandibular space It lies between the internal surface of the mandibular branch & medial pterigoid m. Contents: inferior alveolar nerve & homonymous artery & vein. Communications: interpterigoid space, temporo-pterigoid space & space of the bucal fat body.

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40 Lies between ramus of mandible and medial pterygoid

41 g) Pterygopalatine fossa h) space of the bucal fat body in front of the anterior border of the buccinator m.. It gives the processes which enter: the subaponeurotic space of the temporal region, pterygopalatine fossa & pterygomandibular space. Contents: maxillary artery with its branches, pterygopalatine ganglion & venous plexus.

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43 h) space of the bucal fat body It lies in front of the anterior border of the buccinator m.. It gives the processes which enter: the subaponeurotic space of the temporal region, pterygopalatine fossa & pterygomandibula r space.

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47 Normal TMJ Function When the mouth opens, two distinct motions occur at the joint. The first motion is rotation around a horizontal axis through the condylar heads. The second motion is translation. The condyle and meniscus move together anteriorly beneath the articular eminence. In the closed mouth position, the thick posterior band of the meniscus lies immediately above the condyle. As the condyle translates forward, the thinner intermediate zone of the meniscus becomes the articulating surface between the condyle and the articular eminence. When the mouth is fully open, the condyle may lie beneath the anterior band of the meniscus.

48 Functions of TMJ

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50 Internal structures of the TMJ 1. Articular disc -biconcave, thicker on outside edges - no vascular or nervous supply except at edges - made of fibrous tissue 2. Joint cavities - TMJ is a compound joint a. inferior - below the disc b. superior - above the disc 3. Retrodiscal tissue - superior retrodiscal lamina attaches to glenoid fossa and pulls disc back when mandible opens

51 Internal structure Of TMJ

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57 It acts as unique joint: - complex & combined

58 Biomechanics of the TMJ Two distinct joint systems: 1. Rotational movement - inferior joint cavity 2. Translational movement - superior joint cavity

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74 Sublingual space Between mucous membrane of floor of mouth and mylohyoid and hyoglossus

75 The skin of face is very thin and connected to the facial bones by loose connective tissue. There is no deep fascia. The facial muscles lie in this connective tissue.

76 END