Structure Week 1: LO's

LO 1: Describe the bones and muscle layers of the chest wall

Bones

• sternum: manubrium, body, xiphoid process (T10)

• Ribs (12 pairs)

• Thoracic vertebrae (T1-T12)

Muscle Layers

• Intercostal muscles: external intercostals, internal intercostals, innermost intercostals

• Diaphragm

• superficial: pec major & minor

LO 1: what are the 3 components of the sternum

• manubrium → The superior portion featuring the jugular (suprasternal) notch and the sternoclavicular joints where it articulates with the clavicles

• body → The middle portion of the sternum articulating with ribs 2 through 7

• xiphoid process → The inferior-most portion, located at the level of T10, which may ossify and fuse with the body in adulthood

LO 1: what are the 3 components of the manubrium

• Jugular (suprasternal) notch → superior portion of sternum

• Sternoclavicular joint → where sternum articulates with clavicles

• Sternal angle (T4/T5) → critical clinical landmark formed by the junction of the manubrium and the body

LO 1: what is a subcomponent of the xiphoid process

Xiphisternal joint → The articulation between the xiphoid process and the sternal body

LO 2: what are the 3 classification of ribs & their locations

• True ribs (1-7) → Attach directly to the sternum through their own costal cartilages

• False ribs (8-10) → Their costal cartilages attach to the cartilage of the rib above, forming the costal margin

• Floating ribs (11-12) → Have no anterior attachment and end in the posterior abdominal musculature

LO 2: What are the features & landmarks of the ribs

• head → Features superior and inferior articular facets for articulation with two adjacent vertebral bodies

• neck → Articulate with the transverse process of the vertebra of the same number

• tubercules → Articulate with the transverse process of the vertebra of the same number

• angle → The point where the rib turns anterolaterally/the site of greatest curvature and most common fracture

• costal groove → Located on the internal surface of the inferior border, it protects the intercostal neurovascular bundle

LO 2: what are the 4 atypical ribs

• 1st Rib: Broadest, shortest, and most curved; has grooves for the subclavian vessels.

• 2nd Rib: Has a tuberosity for the serratus anterior muscle.

• 11th and 12th Ribs: Short, rudimentary, and lack a neck or tubercle

LO 2: what does the head of a rib include

Superior/ inferior articular facets

Lo 2: what are the articulations & attachments of the ribs

• Posterior articulations (costotransverse joint & costovertebral joint)

• Anterior articulations (costocondral joint & sternocondral joint)

• Costal cartilage

LO 2: Posterior articulations of ttibs

• Costotransverse joint

• Costovertebral joint

LO 2: Anterior articulations of ribs

• Costochondral joint

• Sternochondral joint

• costal cartilage

Thoracic Vertebrae

Thoracic vertebrae

Recognize cervical vs thoracic vs lumbar vertebrae (include numbers)

LO 3: what are the muscle layers of the chest wall

intercostal muscles

• external intercostals → outermost

• internal intercostals → middle

• innermost intercostals → deepest

diaphragm

LO 3: describe the primary muscles of respiration & innervation

• diaphragm: primary muscle of respiration, separating the thoracic and abdominal cavities. Diaphragm: Innervated by the Phrenic Nerve (C3, C4, C5)

• intercostal muscles: (External, Internal, and Innermost) stabilize the rib cage during the respiratory cycle

• These intercostal muscles are innervated by the intercostal nerves, which are the ventral rami of spinal nerves T1 through T11

LO 3: what are the innnervations of the primary muscles of respiration

• Diaphragm: Innervated by the Phrenic Nerve (C3, C4, C5).

• Intercostal Muscles: Innervated by the Intercostal Nerves (T1-T11

LO 3: functions of intercostal muscles

stabilize intercostal spaces during respiration

LO 4: what are the borders of the thoracic cavity

• Superior (Thoracic Inlet): Bounded by the T1 vertebra, 1st ribs, and the manubrium

• Anterior border: Formed by the sternum and costal cartilages.

• Lateral borders: Formed by the 12 pairs of ribs and intercostal muscles.

• Posterior border: Formed by the 12 thoracic vertebrae and intervertebral discs.

• Inferior border: Formed by the diaphragm

LO 4: anterior border of thoracic cavity

Formed by the sternum and costal cartilages

LO 4: lateral borders of thoracic cavities

Formed by the 12 pairs of ribs and intercostal muscles

LO 4: posterior border of thoracic cavity

Formed by the 12 thoracic vertebrae and intervertebral discs

LO 4: inferior border of thoracic cavity

Formed by the diaphragm

LO 3: Accessory muscles for inspiration & expiration

Accessory Muscles (Forced Breathing):

• Inspiration: Sternocleidomastoid (elevates sternum) and Scalenes (elevate top ribs).

• Expiration: Abdominal muscles (rectus abdominis, obliques) push the diaphragm up

LO 4: mediastinum & pleural cavities

Spaces Within:

• Mediastinum: The central compartment housing the heart and great vessels.

• Pleural Cavities: Two lateral compartments housing the lungs

LO 5: what do the intercostal nerves provide to the chest wall

The intercostal nerves provide both segmental motor and sensory innervation to the chest wall

LO 5: describe the myotomes & dermatomes of the chest wall

• Dermatomes: These represent the segmental areas of skin innervated by the somatic sensory fibers of each intercostal nerve.

- area of skin supplied by one spinal nerve aka skin map (lets you feel pain, touch, temperature)

- think DERM = SKIN

• Myotomes: These represent the groups of muscles (primarily intercostals) innervated by the somatic motor fibers of each intercostal nerve

- group of muscles supplied by one spinal nerve aka muscle map (lets you move muscles)

- think MYO = MUSCLE

LO 5L High yield dermatome landmarks

• T4 dermatome → skin around the nipple

• T10 dermatome → skin around the belly button (umbilicus)

LO 6: Identify the components and location of the intercostal bundle (on rib & intercostal muscles)

• Intercostal Bundle (V.A.N) The neurovascular bundle is organized from superior to inferior as the intercostal vein, intercostal artery, and intercostal nerve.

• Location: It is situated within the costal groove along the inferior border of each rib, running between the internal and innermost intercostal muscles

what kind of fibers are in intercostal nerves & describe them

1) Somatic motor fibers to skeletal muscle (intercostal muscles)

2) Somatic sensory fibers from skin (pain, temperature, touch) and from joints, skeletal muscles, and tendons (proprioception)

3) Sympathetic fibers to sweat glands, arrector pili muscles, and blood vessels in the skin

LO 6: components and location of the intercostal bundle as it relates to clinical procedures [where would you place a chest tube]

Thoracentesis and Chest Tube placement: To avoid damaging the V.A.N bundle, needles or tubes must be inserted close to the upper border of the lower rib

LO 6: components and location of the intercostal bundle as it relates to clinical procedures [where would you do an intercostal nerve block]

Intercostal nerve block: Involves injecting anesthesia to target the large nerve on the underside of the rib

where does the internal thoracic artery run

Internal thoracic artery: Runs vertically on the internal aspect of the anterior thoracic wall

where does the internal thoracic vein drain into and where does this flow

Internal thoracic vein: Drains into the brachiocephalic veins, which then flow into the superior vena cava (SVC)

what does the azygous venous system drain and where does it empty into & what veins are involved

• Azygos Venous System: This system drains the posterior chest wall and empties into the superior vena cava

• azygous vein, accessory hemiazygos vein, hemiazygos vein

azygous vein what is it and which side

Azygos vein: The main vessel of the system on the right side

accessory hemiazygos vein where does it drain and on what side

Accessory hemiazygos vein: Drains the superior portion of the left posterior wall

• Accessory = Above

• “Leave heavy jewlery & accessory’s at home”

hemiazygos vein where does it drain and what side

Hemiazygos vein: Drains the inferior portion of the left posterior wall

LO 7: somatomotor pain innervation in the chest wall what is it provided by (nerves & where include thoracic vertebrae levels), what does this control

• Somatomotor: Provided by somatic motor fibers in the intercostal nerves (ventral rami T1-T11) to the intercostal muscles

• Control the intercostal muscles for breathing

LO 7: somatosensory pain innervation in the chest wall what is it provided by, what sensation are carries and what carries the sensations

Somatosensory pain innervation: Provided by somatic sensory fibers in the intercostal nerves, which carry sensations of pain, temperature, and touch from the skin and proprioception from joints and muscles

LO 7: sympathetic innervation of the chest wall what do the intercostal nerves carry

• Sympathetic innervation: Intercostal nerves carry sympathetic fibers to targets in the skin, including sweat glands, arrector pili muscles, and blood vessels

LO 7:sympathetic innervation sympathetic pathway [where do the signal originate, where do they pass through, and where do they reach, after that where do they exit & to join what to reach where]

Sympathetic Pathway: Signals originate in the lateral horn of the spinal cord, pass through the ventral root, spinal nerve, and white ramus communicans to reach the sympathetic trunk. They then exit via the gray ramus communicans to join the ventral or dorsal rami to reach the body wall

LO 8: imaging modalities for evaluating the chest wall [projectional radiography x-ray PA vs AP describe what view they are, which view is preffered & why, and what they are used for]

• Projectional radiography (X-ray): Uses radiation to create 2D images

• PA (posteroanterior) is the preferred view as it prevents heart size exaggeration

• AP (anteroposterior) is often used for bedbound patients

LO 8: imaging modalities for evaluating the chest wall computed tomography (CT and CTA) what does it do

• Computed Tomography (CT and CTA): Obtains tomographic "slices" that can be reconstructed into 3D images for detailed diagnostic evaluation

• Excellent for seeing detailed anatomy and tumors

• CTA (CT Angiogram): Uses contrast dye to see blood vessels, like the aorta or pulmonary arteries

LO 8: imaging modalities for evaluating the chest wall fluoroscopy

• Fluoroscopy: Provides real-time moving images, useful for procedures like esophageal exams or cardiac catheterization

• Used for moving structures like the heart during catheterization

LO 8: imaging modalities for evaluating the chest wall ultrasound

Ultrasound: Can be used to visualize pleural fluid or guide procedures like thoracentesis

LO 8: what are the 2 high yield x-ray signs

• Silhouette Sign: Loss of a normal border (like the heart edge) means something dense (like pneumonia) is touching it.

• Pneumothorax: Shows as a dark area with no lung markings

LO 9: cartilage is an ______ tissue formed from mesoderm via ___________

General Features: Cartilage is an avascular connective tissue formed from mesoderm via chondrogenesis

LO 9: what are the 2 types of cartilage cells

Cells:

• Chondroblasts: Located near the perichondrium, they secrete the extracellular matrix.

• Chondrocytes: Mature cells situated in lacunae; often seen in groups called nest cell

LO 9: what are the 3 types of cartilage

• hyaline cartialge

• elastic cartilage

• fibrocartilage

LO 9: hyaline cartilage what does it contain, what type of collagen, where is it found, what is it a precursor of

• Hyaline cartilage: The most common type with a homogeneous matrix containing type II collagen and aggrecan.

• Found in the ribs (costal cartilage), nose, larynx, and trachea; it has a perichondrium

• it’s a precursor of bone

LO 9: elastic cartilage what type of collagen, what does it contain, where is it found

• Elastic cartilage: Contains type II collagen and a dense network of dark-staining elastic fibers.

• Found in the external ear, larynx, & epiglottis; it also has a perichondrium

LO 9: fibrocartilage what is it a mixture of, what type of collagen, what does it lack, & where is it found

• Fibrocartilage: A mixture of hyaline cartilage and dense regular connective tissue (type I collagen).

• It is the strongest type, lacks a perichondrium, and is found in intervertebral discs, joint capsules, and ligaments

LO 10: bone matrix what is it comprised of organic vs inorganic part

Bone Matrix: Comprised of an organic part (90-95% type I collagen) and an inorganic part (hydroxyapatite crystals of calcium and phosphate)

LO 10: what are the 4 bone cells

• osteoprogenitor cells

• osteoblasts

• osteocytes

• osteoclasts

LO 10: osteoprogenitor cells where are they found and what do they differentiate into

Osteoprogenitor cells: Stem cells found in the periosteum and endosteum stem cells that become osteoblasts

LO 10: osteoblasts what type of cells and what do they form

Osteoblasts: Cuboidal cells that form new bone by secreting the organic matrix

LO 10: osteocytes where are they found & their communication

Osteocytes: Mature bone cells found in lacunae; they communicate through thin processes called filopodia via gap junctions

LO 10: osteoclasts what are they responsible for

• Release acid, collagenase , and other lytic enzymes to break down bone matrix and release minerals (bone resorption).

• Osteoclasts: Large, multinucleated cells responsible for bone resorption (breaking down matrix); they sit in Howship's lacunae

LO 10: what are the 2 types of bones

• compact (cortical) bone

• cancellous (spongy/trabecular) bone

LO 10: compact (cortical/dense bone) what it is, where is it found, what is it organized into

• Compact (cortical) bone: Dense bone lacking large spaces, found in the diaphysis of long bones.

• It is organized into osteons with concentric lamellae surrounding a Haversian cana

• Made of Osteons (Haversian systems) which look like tree rings

LO 10: Cancellous (spongy/trabecular) bone what it is and what does it surround

Cancellous (spongy/trabecular) bone: A 3D lattice of bony slips called trabeculae, which surround spaces containing bone marrow

LO 10: primary (woven bone) vs secondary (lamellar) bone

• Primary (woven) bone: The first randomly arranged bone tissue to appear during development or repair; it is eventually replaced.

• Secondary (lamellar) bone: Mature, highly organized bone tissue

LO 10: bone development (ossification) 2 types

• intramembranous

• endochondral

LO 10: bone development (ossification) intramembranous

Intramembranous: Bone develops directly from membranes (e.g., flat skull bones

LO 10: bone development (ossification) endochondral

Endochondral: Bone replaces a pre-existing cartilage model (e.g., long bones of limbs)