Chapter 6: Vascular Supply

1. Chapter 6: Vascular Supply

2. Blood Distribution • 60% of blood volume at rest is in systemic veins and venules • function as blood reservoir • blood is diverted from it intimes of need • increased muscular activityproduces venoconstriction • hemorrhage causes venoconstriction to help maintain blood pressure • 15% of blood volume in arteries & arterioles

3. Cardiovascular System Blood vessels: Types A. Arteries -carry blood away from heart -thicker than veins -three layers: inner endothelium middle smooth muscle outer connective tissue -arteriole = small artery B. Veins -carry blood toward heart -same three layers as arteries (less SM and connective tissue) -thinner and more expansive than arteries -contain valves - to help the flow of blood back to heart -small vein = venule C. Capillaries -site of gas exchange with tissues -connect arterioles and venules -network of microscopic vessels (one cell thick) = capillary bed -site of exchange: gases, nutrients, wastes -can be closed off when not needed

4. Arteries • Tunica interna (intima) • simple squamous epithelium known as endothelium • basement membrane • internal elastic lamina • Tunica media • circular smooth muscle & elastic fibers • smooth muscle is innervated by sympathetic nervous system • decrease in stimulation or presence of certain chemicals causes vasodilation • increases diameter of vessel • nitric oxide, K+, H+ and lactic acid cause vasodilation • increase in stimulation causes muscle contraction or vasoconstriction • decreases diameter of vessel • Tunica externa • elastic & collagen fibers

5. Elastic Arteries • Largest-diameter arteries have lot of elastic fibers in tunica media • Help propel blood onward despite ventricular relaxation (stretch and recoil -- pressure reservoir) Muscular Arteries • Medium-sized arteries with more muscle than elastic fibers in tunica media • Capable of greater vasoconstriction and vasodilation to adjust rate of flow • walls are relatively thick • called distributing arteries because they direct blood flow

6. Veins • Proportionally thinner walls than same diameter artery • tunica media less muscle • lack external & internalelastic lamina • Still adaptable to variationsin volume & pressure • Valves are thin folds of tunica interna designed to prevent backflow • Venous sinus has no muscle at all • coronary sinus or dural venous sinuses • are large blood-filled spaces between two layers of tissue e.g. dural sinus – between the two layers of the dura mater meninges

7. Capillaries • Microscopic vessels that connect arterioles to venules • Found near every cell in the body but more extensive in highly active tissue (muscles, liver, kidneys & brain) • entire capillary bed fills with blood when tissue is active • lacking in epithelia, cornea and lens of eye & cartilage • Function is exchange of nutrients & wastes between blood and tissue fluid • Structure is single layer of simple squamous epithelium and its basement membrane

8. Common Carotid • -no branches as it travels up the neck • lateral to the trachea and larynx • beneath the sternocleidomastoid • wrapped in a sheath with the internal jugular and vagus nerve • ends in two divisions: • 1. internal carotid • 2. external carotid • just before the bifurcation – swelling = carotid sinus

9. Internal carotid • Internal carotid arteries (contribute to Circle of Willis) • lateral to the external carotid • branchless as it travels up the neck • at the base of the skull – forms the Circle • of Willis • supplies the brain • also gives off an opthalmic branch • supplies the eyes, orbits, and lacrimal gland

10. Common Carotid Branches • External carotid arteries • supplies structures external to skull as branches of maxillary and superficial temporal branches • 8 branches divided into four portions: • anterior portion • ascending portion • posterior portion • terminal portion

11. External carotid • 1. anterior portion: • Superior thyroid • Lingual • Facial (external maxillary) • 2. ascending portion • Ascending pharyngeal • 3. posterior portion • Occipital • Posterior auricular • 4. terminal portion • superficial temporal • maxillary (internal maxillary “Seven Little Fairies Ascended Over Polly’s Super Mums”

12. External Carotid artery 16 – infraorbital 17 – internal maxillary 10 – descending palatine 29 – superficial temporal 9 – deep lingual (lingual) 15 – inferior labial (facial) 24 – sublingual (lingual) 20 – middle meningeal (maxillary) 28 – superficial temporal 22 – posterior auricular 2 – ascending palatine (facial) 21 – occipital 18 – lingual 11 – facial 6 – carotid, external

13. Superior thyroid -supplies the infrahyoid region - muscles of the larynx, and thyroid -branches: infrahyoid sternocleidomastoid superior laryngeal superior and inferior thyroid Lingual -supplies the suprahyoid region, floor of mouth and tongue -branches: deep lingual – apex of tongue dorsal lingual – base and body of tongue sublingual – mylohyoid, sublingual gland, mucous membranes of mouth floor suprahyoid - suprahyoid muscles

14. 9 – deep lingual 24 – sublingual 26 – submental 18 – lingual artery 6 – external carotid

15. Facial = external maxillary -can have a common trunk with the lingual -runs medial to the mandible -over the submandibular gland -over the lateral side of the mandible (under the platysma) -parallels the facial vein – separated by the posterior belly of the diagastric -divided into cervical and facial branches Facial branches inferior labial – lower lip and its muscles superior labial – upper lip and its muscles angular – side of nose, ends a medial commisure muscular Cervical branches ascending palatine – soft palate and palatine muscles submandibular/glandular – glandular tissues submental – submandibular lymph nodes, submandibular salivary gland, mylohyoid and diagastric tonsillar – palate and roof of mouth

16. Facial artery (external maxillary) 16 – infraorbital 10 – descending palatine 27 – subnasal 29 – superior labial 15 – inferior labial 26 – submental 17 – internal maxillary 14 – inferior dental 25 – submandibular gland (glandular)

17. Ascending pharyngeal -ascending portion of external carotid -several small branches 1. palatine – may replace the ascending pharyngeal of the facial artery 2. pharyngeal – pharynx 3. meningeal – meninges 4. inferior tympanic – with the glossopharyngeal nerve, it enters the temporal bone to supply the tympanic region • Posterior auricular • auricular branch – internal ear • stylomastoid branch – mastoid air cells • occipitalis branch – occipitalis muscle and scalp at back of head • -may join with the occipital artery

18. Occipital -arises near the hypoglossal cranial nerve (XII) -travels to and supplies the posterior scalp -branches: 1. muscular – diagastric, stylohyoid splenius, and long. capitis 2. meningeal – through the jugular f. supplies the dura mater in the posterior fossa 3. SCM – may arise directly from the EC supplies the SCM 4. descending – largest branch, descends along the back of the neck, supplies the trapezius and semispinalis capitis 5. auricular – supplies the conchae and dura mater, enters via the stylomastoid foramen

19. Superficial temporal 1. transverse facial – runs along zygomatic arch -supplies the parotid gland, cheek bone and masseter 2. middle temporal – runs along the zygomatic arch, -supplies the temporalis 3. anterior auricular – supplies the outer ear structures 4. frontal – supplies the frontalis, front scalp 5. parietal – supplies muscles of the parietal region

20. Internal Maxillary -largest of the terminal branches of the external carotid -begins at neck of mandibular condyle -can be divided into three portions it arises from the EC 1. Mandibular 2. Pterygoid 3. Pterygopalatine

21. 1. Mandibular portion a. anterior tympanic b. middle meningeal – largest branch, supplies the dura mater, thru the foramen spinosum c. deep auricular – branch to the TMJ, supplies the tympanic membrane d. accessory meningeal – thru the foramen ovale, supplies the dura mater e. inferior alveolar – thru the mandibular f. with the inferior alveolar nerve, travels thru the mandibular canal -gives off four main branches 1. myloyoid branch – branches off before it enters the mandibular canal, supplies the floor or mouth and mylohyoid 2. lingual branch – supplies the mucus membranes of the mouth 3. mental branch – exits thru the mental f., supplies the chin 4. incisive branch – divides about the first premolar into dental and alveolar branches -dental = pulp tissue -alveolar = peridonteum + gingiva

22. 2. Pterygoid portion • -accompanies the trigeminal cranial • nerve (V) • -branches: • deep temporal – anterior and posterior • temporalis • 2. masseteric • 3. pterygoid – lateral & medial pterygoid m. • 4. buccinator

23. Pterygopalatine portion • -branches: • posterior superior alveolar = post-dental • artery • -gives off dental and alveolar branches • -supplies the premolars and molars • -also the lining of the maxillary sinuses • b.artery of the pterygoid canal = vidian artery • -upper pharynx and auditory canal • c. infraorbital – thru the infraorbital f., supplies facial structures • -gives off an orbital branch and a superior alveolar branch (dental and alveolar branches) • d. pharyngeal – upper pharynx and auditory tube • e. sphenopalatine – thru the sphenopalatine f., enter the nasal cavity • -supplies the nasal conchae, the anterior part of the hard palate, the ethmoid, maxillary • and frontal sinuses (lateral nasal branch) • -also supplies the nasal septum (posterior septal branch)

24. -so dental and alveolar branches come from 1. the incisive branch of the inferior alveolar (mandibular portion) 2. posterior superior alveolar – pterygopalatine portion 3. anterior superior alveolar branch of the infraorbital (pterygopalatine portion) -supplies the upper incisors & canines -plus the maxillary sinus

25. Veins of the Head and Neck • External and Internal jugular veins drain the head and neck into the superior vena cava • Dural venous sinuses empty into internal jugular vein

26. Veins of the Head and Neck • Frontal • Supraorbital • Angular • Superficial temporal • Internal maxillary • Posterior Facial • Posterior Auricular • Occipital

27. Facial Vein • drains into the internal jugular • begins at the medial corner of the eye • forms from the union of supratrochlear and supraorbital veins (drains the orbit) -also connects with the: -superior labial -inferior labial -submental – chin and submandibular region -lingual (dorsal, deep/ventral, sublingual branches) • two major branches: • retromandibular • superior thyroid -joins with the pterygoid plexus -union of the meningeal, posterior superior alveolar branches + branches from the nasal region and palate -drains the deep portions of the face & meninges

28. Retromandibular Vein -forms from the superficial temporal and maxillary veins -emerges from the parotid gland and travels down the neck -below the parotid – divides into two branches 1. anterior division – drains the facial region 2. posterior division – drains the facial region, travels down the SCM -the posterior division is joined by the posterior auricular vein = External Jugular

29. Superficial Temporal -drains the lateral scalp -joins up with the retromandibular vein • Maxillary • -drains the pterygoid plexus • -merges with the superficial temporal – into the retromandibular vein • -forms from the: • posterior superior alveolar – dental and alveolar branches (maxillary arch) • inferior alveolar – dental and alveolar branches (mandibular arch) • middle meningeal - meninges