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Introduction to the Head Formation

5 Pages

Course Code
BIOL 1103
Tamy Superle

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Introduction to the Head I. Function a. House/protect brain, meninges, and special sense organs b. Respiration c. Mastication (chewing) & deglutition (swallowing) d. Vocalization  II. Scalp a. Layers S kin C onnective Tissue A poneurosis epicranialis(galea aponeurotica): joins frontalis m to occipitalis m L oose connective tissue (areolar space): layer in which scalp moves relative to skull; is UNDER muscles * infections spread easily in this layer P ericranium (periosteum) b. Diploe of parietal bone: spongy layer of bone containing red marrow and diploic veins (network w/in cranial bones that communicates with veins going between skin and brain *important in spread of infection* i. Diploic veins: run within cranial bones ii. Emissary veins: pass thru cranial bones from brain to surface III. Skull a. Bones: 21 bones + mandible + hyloid + (3 ear bones)x2 = 29 bones in skull b. Parts i. Cranium: skull without mandible ii. Neurocranium: “top” of skull; above eyes, ears, and posterior aspect 1. Bones: frontal, parietal (2), occipital (squamous portion), temporal (2) (squamous portion), sphenoid (greater wing) iii. Basicranium: inferior support of brain; contribute to interorbital region (area beween eyes and superior to nasal passages) 1. Bones: occipital, temporal, ethmoid, sphenoid (lesser wing and pterygoid plate iv. Viscerocranium (splanchnocranium): bones of face (including mandible) 1. Bones: maxilla (2), palatine (2), zygomatic (2), lacrimal (2), nasal (2), vomer, mandible, inferior nasal concha (2), Auditory Ossicles – malleus, incus, & stapes (2 each), hyoid. c. “Joints” i. Sutures: Coronal, sagittal, lamdoidal, squamosal, lambda, bregma, intermaxillary, metopic (superior to nasion) ii. Fontanelles: anterior, posterior, posteriolateral (mastoid), anteriolateral (sphenoid), d. Cavities i. Endocranial Cavity: contains brain/meninges/CSF/vascular supply 1. numerous foramina (holes allowing passage of neurovascular bundles) a. Foramen magnum= exit of sp. cord from endocranial cav. 2. floor is subdivided into fossae a. anterior fossa: contains front lobes of brain b. middle fossa: contains paired temporal lobes c. posterior fossa: contains cerebellum & brainstem ii. Orbits (2) iii. Nasal Cavities iv. Oral Cavity v. Middle Ear Cavities IV. Gross Anatomy of the Brain a. Telencephalon (cerebrum) i. Left and right hemispheres separated by longitudinal fissure ii. Basal ganglia: nuclei in ventral telencephalon that control diff. fxns. iii. Four lobes: Frontal, Parietal, Temporal, Occipital iv. Gyri: folds of brain tissue covering external surface (singular = gyrus) v. Sulci: shallow grooves separating gyri (singular = sulcus) b. Diencephalon: (Thalamus, hypothalamus, epithalamus, subthalamus) i. “central core” of brain; almost completely encased in telencephalon ii. only visible from an inferior view of the infundibulum (pituitary location) iii. CN II comes from here (optical tract) c. Mesencephalon (midbrain) i. Contains inferior and superior colliciul (vision and hearing) ii. Cerebral aqueduct runs through it iii. Invisible from outside d. Pons (“Pons” = “bridge” in Latin) i. Trigeminal N. (CN V) originates in pons e. Medulla Oblongata i. Continuous with spinal cord ii. Abducens (CN VI), Facial (CN VII), & Vestibulocochlear (CN VIII) originate at jxn between medulla oblongata and pons iii. Glossopharangeal (CN IX), Vagus (CN X), Accesory (CN XI), & Hypoglosseal (CN XII) originate from lateral aspects of med. oblong. f. Cerebellum i. Two hemispheres ii. Responsible for much motor function V. Ventricle System and Meninges a. Ventricle System i. Def: series of cavities/passages within brain filled with CSF ii. Lateral—(R & L) lg cavities w/in cerebral hemispheres iii. Interventricular Foramen—path between each lateral and 3 ventricles iv. Third Ventricle—between R/L parts of diencephalons rd th v. Cerebral Aqueduct—path between 3 & 4 ventricles vi. Fourth Ventricle—in pons/ med. oblong.; continuous w/ central sp. canal b. CSF (Cerebrospinal Fluid) i. Fxn: cushion, bathe, & nourish the brain ii. Continuously produced & turns over ~4-5 x per day iii. Choroid plexuses—specialized type of pia mater lining ventricles that produce CSF iv. Circulation: Lateral Ventricles → interventricular foramen → 3 rd ventricle → cerebral aqueduct → 4 ventricle → median/lateral apertures →subarachnoid space →arachnoid granulations →drains into venous circ. v. Arachnoid Granulations: protrusions from arachnoid layer into venous sinuses; act as one-way, pressure-sensitive valves passing CSF into venous sinuses c. Meninges i. Def: layers of connective tissue providing support, protection, & nourishment to brain; continuous w/ meninges of spinal cord ii. Pia Mater: (innermost layer) transparent, highly vascularized, adheres to surface of brain; contains vessels supplying brain iii. Arachnoid Mater: (middle layer) thin layer bridging sulci => fluid filled subarachnoid spaces located mainly at base of brain (cisterns) iv. Dura Mater: (external layer) tough, dual-layered membrane 1. Outer: (periosteal) adheres tightly to the skull 2. Inner: normally fused with outer, but also separates in some places to form venous sinuses or enclose meningeal vessels 3. Dural folds: double-layer of inner mater adhered to itself a. Falx cerebri: vertical, between two cerebral hemispheres; houses superior/inferior sagittal sinuses b. Tentorium cerebelli: horizontal; separates cerebellum
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