Anatomy Lecture Notes Flashcards

Spinal Cord

• For the Friday lecture, the location will be in Hamilton Hall 250 due to construction.
• Announcements will be sent out on Wednesday to remind everyone of the room change.
• Homework and practice quizzes should be completed to assess understanding.
• The exam is next Wednesday.

Spinal Cord Anatomy

• The dorsal or posterior section is towards the top.
• The ventral section is towards the bottom, also known as the anterior section.
• Sensory information is afferent, arriving in the central nervous system.
• Motor information is efferent, exiting the central nervous system.

Motor Neurons

• Cell bodies are in the central nervous system, specifically in the ventral horn (gray matter).
• Axons exit via the ventral root and reach effectors in the body.
• After the ventral root the signal goes to the spinal nerve
• From the spinal nerve the axons can go through the dorsal or ventral ramus
• Some axons go to the deep back muscles via the dorsal ramus (e.g., erector spinae muscles).
• Most axons go to the limbs, trunk region, and anterior body via the ventral ramus.
• The motor signal is efferent.

Sensory Neurons

• Sensory information (e.g., pat on the back) is transmitted via sensory neurons.
• Axons travel through the dorsal ramus into the spinal nerve.
• The dorsal root ganglion contains cell bodies of sensory neurons.
• Axons bypass the cell body and enter the dorsal root, then the dorsal horn.
• Information from the rest of the body (e.g., ant walking on arm) enters via the ventral ramus.
• It goes into the spinal nerve, bypasses the cell body in the dorsal root ganglion, enters the dorsal root, and goes to the dorsal horn.
• Sensory information is afferent.

Interneurons

• Cell bodies are in the dorsal horn.
• They can send signals up to the brain or create a reflex arc, connecting to motor neurons.
• Interneurons communicate within the central nervous system.

Information Flow

• Ventral horn and ventral root carry only motor information.
• The spinal nerve, ventral ramus, and dorsal ramus contain both motor and sensory information.
• The dorsal root ganglion, dorsal root, and dorsal horn are mostly sensory but connect with interneurons.
• The posterior path is sensory.

Spinal Cord Features

• The dorsal rami is tiny compared to the ventral rami and goes to deep back muscles and a small patch of skin.
• The ventral rami goes to everything else in the body.
• The roots indicate what is being carried (sensory or motor), and the rami indicate where things are going.

Spinal Cord Cross-Section

• Different parts of the white matter carry specific types of information and are organized into tracts or vesiculi.

Cross-Section Analysis

• A particular region is carrying motor information as it is anterior (ventral) with motor cell bodies.
• Motor information is efferent and exiting the area.
• This region is specifically the ventral root.
• The spinal nerve contains both motor and sensory information (mixed).

Spinal Cord Anatomy Review

• The posterior indent on the spinal cord is the posterior (dorsal) median sulcus.
• The deeper anterior indent is the anterior median fissure.
• The bulge is the dorsal root ganglion.
• The opening is the central canal, containing cerebrospinal fluid (CSF).
• Gray matter contains cell bodies and unmyelinated axons, located centrally.
• White matter contains myelinated axons for fast information travel (e.g., to and from the brain).

Sensory Information Pathway

• Information comes from the back via the dorsal ramus or from the rest of the body via the ventral ramus.
• It then goes into the spinal nerve, bypasses the sensory cell body in the dorsal root ganglion, and enters the dorsal root and dorsal horn.
• From there, interneurons send information to the brain or create a reflex arc with motor neurons.
• Sensory information enters the central nervous system.

Homunculus and Arteries

• Sensory information enters the spinal cord and goes up to the postcentral gyrus in the brain (sensory cortex).
• Middle cerebral artery (from the internal carotid) serves part of this area.
• The anterior cerebral artery also serves part of this region.
• The posterior cerebral artery also serves part of this region.
• The anterior cerebral artery covers the lower limb and back areas.
• The middle cerebral artery covers the face region.
• A blood clot affecting the middle cerebral artery may cause face sensory/motor problems, while one affecting the anterior cerebral may cause lower limb problems.

Example Pathway

• Sensory information from the right upper limb travels through the ventral ramus into the spinal nerve.
• It bypasses the dorsal root ganglion and travels through the dorsal root to enter the dorsal horn.
• An interneuron sends the axon up through the spinal cord, crossing over to the left side of the brain since it's coming from the right hand.
• It reaches the postcentral gyrus (sensory cortex).
• Information from the lower limb is found in the area of the brain supplied by the anterior cerebral artery.
• Sensory information from the back goes into the dorsal ramus.
• The true back refers to deep back muscles and a strip of skin associated with the dorsal ramus.
• The back area on the homunculus is colored in blue and is a small part wrapping over that area of the cortex, covered by the anterior cerebral artery.

Muscles of Facial Expression

• Innervated by cranial nerve number 7 (facial nerve).
• The origin is on the skull and the insertion is on the skin and fascia of the face.

Branches of the Facial Nerve

• Temporal.
• Zygomatic.
• Buccal (bule).
• Marginal Mandibular (mandibular).
• Cervical.
• Mnemonic: "To Zanzibar by motor car."

Muscles

• Frontalis:
  • Anteriorly on the frontal bone.
  • Action: Raise eyebrows, wrinkle forehead.
• Occipitalis:
  • Posteriorly on the occipital bone.
  • Action: Draw the scalp posteriorly.
• These share an aponeurosis (tendinous sheet) and are sometimes called occipitofrontalis.
• Orbicularis Oculi:
  • Surrounds the eye.
  • Action: Close the eye, pinch the eye shut, wink.
• Orbicularis Oris:
  • Surrounds the mouth.
  • Action: Close the lips, protrude lips (duck face).
• Buccinator:
  • Muscle of the cheek area.
  • Branches of the facial nerve: Buccal or bule
  • Action: Press the cheek in towards the teeth.
  • Used in eating, blowing air, and whistling.
  • The parotid duct (from the parotid gland) pierces this muscle and enters the mouth by the 2nd top molar.
• Platysma:
  • Spreads out over the neck region (cervical).
  • Action: Tense the skin of the neck, lower the inferior part of the lip.
  • Difficult to see in the lab.

Muscle Actions

Orbicularis oris is used for: duck face.

Platysma is used for: the frilled lizard neck.

Orbicularis oculi is used for winking.

Frontalis and Occipitalis can be used for: raised eyebrow.

Muscles of Mastication

• Innervated by cranial nerve number 5 (trigeminal), specifically V3 (mandibular division).

Function

• Move the temporomandibular joint (TMJ).
• TMJ has rotation (small movements) and sliding (large opening) motions.
• Elevate the mandible

Muscles

• Temporalis, masseter, medial pterygoid, and lateral pterygoid.
• Temporalis:
  • Covers the temporal region and attaches to the coronoid process of the mandible.
  • Action:
    • Elevate (anterior section).
    • Retract the mandible.
• Masseter:
  • More inferior and elevates the mandible.
  • Action: Elevate the mandible. It closes the mouth.
• Lateral Pterygoid:
  • Connects to the temporomandibular joint.
  • Action:
    • Protrude the joint (sliding motion).
    • Depress the jaw.
    • Move the mandible side to side.
• Medial Pterygoid:
  • Mirror image to the masseter on the inside of the mandible.
  • Action:
    • Elevate the jaw.
    • Protrude.
    • Aid with side-to-side motion.
• Mnemonic: "The M's munch"; masseter, temporalis and medial pterygoid elevate or close the mouth; and the lateral pterygoid facilitates side-to-side motion.

Other Muscles

• Trapezius and Sternocleidomastoid:
  • Innervated by cranial nerve number 11 (accessory nerve).
  • The trapezius is on the posterior side of the back and is used to elevate, retract and depress the scapula.
  • The sternocleidomastoid is running anterior on the neck.
• Sternocleidomastoid:
  • Serno (sternum).
  • Cleo (clavicle).
  • Mastoid (mastoid process of the temporal bone).
  • Action:
    • Flex the neck anteriorly (bilaterally).
    • Turn the head to the right (contract the left muscle).
  • To look right, contract the left.
• Hyoid Bone:
  • Does not articulate with any other bony feature; floating there in the neck.
  • Serves as a muscle attachment point for swallowing, yawning, and speech.
• Suprahyoid Muscles:
  • Located superior to the hyoid bone.
  • Action:
    • Depress the mandible (open the mouth).
    • Raise the hyoid bone.
• Infrahyoid Muscles:
  • Inferior to the hyoid bone (strap muscles).
  • Action:
    • Stabilize the hyoid.
    • Pull down on the hyoid.

Clinical Application

Orbicularis oris is used for kissing.

The left sternocleidomastoid is used to turn the head to the right.

Blood Vessels of the Head and Neck

• Anterior portion of the brain: supplied by the internal carotid artery.
• Posterior portion of the brain: supplied by the vertebral artery.
• These meet in the circle of Willis.
• Common Carotid Artery:
  • Splits into the internal (to the brain) and external (to the face and neck) carotid arteries.
• Vertebral Artery:
  • Branches off the subclavian.
  • Passes through the transverse foramina of the cervical vertebrae.
  • Enters the brain through the foramen magnum.

Veins

• External Jugular Vein:
  • Superficial to the sternocleidomastoid muscles.
  • Drains the external carotid artery's area.
• Internal Jugular Vein:
  • Runs deeper with the carotid arteries.
  • Drains blood from the brain (sinuses).
  • Deep to the sternocleidomastoid.
  • Large: runs deep.
  • We can see all those um sinuses.
  • Here we have, so here's our confluence of sinuses, we have the transverse sinus, the sigmoid sinus, and then once we come out of the skull here, now it's an actual vein.

Venous Blood Flow

• External jugular drains into the subclavian.
• The subclavian joins the internal jugular to create the brachiocephalic
• Brachiocephalic (right and left).
• Join together to form the superior vena cava.
• The superior vena cava dumps into the right atrium of the heart.