Anatomy of Thorax/ Histology Flashcards
What are the differences between true, false and floating ribs?
True- Ribs 1-7- costal cartilage is attached directly to sternum
False- Ribs 8-10- Costal cartilage attaches to cartilage above it (cartilage creates costal margin)
Floating- Ribs 11, 12- Do not attach to sternum
What forms the superior thoracic aperture?
Superior margin of T1 ribs and manubrium of sternum
What forms the inferior thoracic aperture and what attaches to it?
Diaphragm attaches to it
Formed by inferior margin of floating ribs, costal margin and xiphoid process of sternum
How far up does the diaphragm sit?
Attached to T11
What does the diaphragm attach to?
Inferior thoracic aperture, xiphoid, lumbar vertebrae (1-3)
What innervates the digaphram?
Phrenic Nerve (C3-C5) C3, 4, 5, keep the phrenic nerve alive
What openings are in the diaphragm and what passes through at what level of the ribs?
Caval opening- inferior vena cava at T8, most anterior
Oesophageal Opening- Oesophagus T10
Aortic Hiatus- Aorta (most posterior) at T12
What muscles are in the thoracic wall, what movement does each muscle cause, and when is each set most active?
Internal intercostal- present anteriorly back to angle of ribs. Active during expiration. Pull ribs down
External- Active during inspiration. Pull inferior ribs upward and out.
Innermost intercostal- Incomplete and sparse, associated with internal layer
Where is the neurovascular bundles supplying the intercostal muscles found in terms of depth?
Between the internal and innermost intercostal muscles
What muscles are important for respiration?
Diaphragm moves down
External intercostal move ribs up and out
What accessory muscles aid in exhalation?
Internal intercostal muscles Transverse Thoracis External Obliques Internal Obliques Rectus Abdominus
What accessory muscles aid in inhalation?
Pectoralis minor (via fixing upper limb to help lift ribs)
Sternocleidomastoid
Scalene
Serratus Anterior
Where and what forms the intercostal neurovascular bundles, and where do the nerves stem from?
Run along costal grove at inferior posterior portion of rib.
VAN- Vein (superior- most protected)
Artery
Nerve
Anterior rami of T1-T11 form intercostal nerves
Anterior ramus of T12 forms subcostal (underneath rib 12)
Where do the intercostal arteries stem from?
Posterior- originates from aorta and travels along with nerve
Anterior- originates from internal thoracic artery (branch of subclavian aka mammary)
They will anastomose
Why is the anastomosing of the anterior and posterior intercostal arteries important?
Important in aiding in blood flow to the lower body if there is a blockage of the aorta (blockage can’t be sudden)
Blood will move into anterior intercostal artery, meet with posterior and down, then re-join with aorta lower down
What cavities are found in the thoracic cavity, and what is found in them?
2 Pulmonary- hold lungs, left is smaller
Mediastinum- hold heart, oesophagus, aorta, trachea and separates two pulmonary cavities
What layers of the heart and what are their purpose(s), starting most superficial?
Fibrous pericardium- protective, anchors heart in place
Parietal serous - secrete fluid to reduce friction
Pericardial cavity
Visceral serous pericardium (epicardium)- secrete fluid to reduce friction
Myocardium- contains myocytes for contraction
Subendocardium- Purkinje Fibres are here, connects myocardium and endocardium
Endocardium- Simple squamous cells, helps reduce friction in chambers reducing turbulence, helps form valves
Membranes are continuous
What layers surround the lungs and what are their purpose, starting most superficial?
Parietal Pleura- anchors lungs to thoracic cavity
Pleural cavity- has fluid secreted by serous membrane (pleura)
Visceral Pleura- surrounds lungs
Membranes are continuous
What is serous membrane?
Set of membranes (visceral and parietal) surrounding an organ that allows for lubrication between two membranes helping to reduce friction.
What are the pleural recesses?
Potential spaces between the costal and diaphragmatic pleura that the lungs can move into during inspiration.
Visceral, parietal, costal, diaphragmatic, mediastinal, cervical
What is the costodiaphragmatic recess?
Between costal and diaphragmatic pleura there is a sharp angle at dome of thorax
It is potential space for lung to extend into.
Most inferior part of cavity and where liquid will build
Where is the safest place for a draining chest tube placement, and why?
Just above the 10th rib.
This is where the costodiaphragmatic recess is (where fluid will accumulate), so best for drainage
Above 10th rib- intercostal nerves run along costal groove inferior to ribs, and are more important in function than collateral branches that run superior to ribs.
Can angle needle up to try and avoid collateral branches
What structures do you pass through in order to place a chest tube? Start most superficial.
Skin Subcutaneous fat and Fascia External, internal, innermost intercostal muscles (avoid collateral/ intercostal nerves) Endothoracic Fascia Costal parietal pleura Costodiaphragmatic recess
Starting at the sagittal plane of the body and moving laterally, what are surface landmarks?
Jugular notch at the manubrium down to sternal angle (where rib 2 attaches) Midclavicular line Anterior axillary line Midaxillary line Posterior axillary line
What fissures are found in the lungs?
Horizontal on right lobe- most superior, separating superior and middle lobes
Oblique- separates middle/ inferior right lobe, and superior/inferior left lobe
What is the cardiac notch and lingula?
Cardiac notch is in left lobe where the heart sits
Lingula is a lipping of the inferior medial aspect of the superior left lobe
What hold the lobes in place?
The trachea and structures entering the lobes through the hilum
How do the borders of the right and left lungs differ?
Right has larger posterior border and straight anterior (costal) border.
What structures are found in the hilum of the lungs?
Bronchi Pulmonary arteries Pulmonary veins Nerves Lymphatics (can be quite distinctive and black at the hilum)
What is the arrangement of the structures within the hilum?
Superior- Pulmonary arteries
Inferior- Pulmonary veins (2)
Posterior- Bronchus is posterior to the structures and more superior in right lobe- may also see cartilage around them
Describe the bifurcations that help form the tracheobronchial tree, including first bifurcation location.
Trachea bifurcates at level of sternal angle into primary bronchi (forms carina)
Primary bronchi branch into secondary (lobar) bronchi (3 right, 2 left)
Secondary bronchi branch into tertiary (segmental) bronchi (10 right, 8 left)
Tertiary bronchi supply bronchopulmonary segments
How does the primary bronchus or the right lung differentiate from the left?
Right bronchus is shorter and more vertical
This means if patients aspirate, object is more likely to move into this bronchi
What are the bronchopulmonary segments?
Discrete independently functioning area within the lungs.
They have independent bronchus, pulmonary arteries and veins.
How does blood move through the lungs?
Pulmonary arteries bring deoxygenated blood to lungs
Arterioles -> capillaries
Oxygen exchange results in offloading of CO2 and uptake of O2
Capillaries join -> venules -> veins (have segmental venules that come together to form lobar veins) -> lobar veins form pulmonary veins
2 pulmonary veins on left, 2 on right
Pulmonary veins take oxygenated blood to the left atrium
How is lung tissue supplied?
Bronchiole arteries and veins
Where does the trachea begin and divide?
Begins at C6 below the cricoid cartilage of the larynx
Divides at T4 into two principle bronchi
What structures form the trachea?
C-shaped hyaline cartilage rings anteriorly joined by fibroelastic membrane
Posterior gaps united by trachealis muscle
Inner specialized mucous membrane contains cilia
What is the atrioventricular groove?
Separates the atria from the ventricle, wrapping around posterior portion
Also called coronary sulcus
What separates the right and left ventricles from a superficial posterior and also an anterior view?
Posterior interventricular artery
Anterior interventricular artery (left anterior descending artery)
What portions of the heart does the left anterior descending artery supply?
Left and right ventricle
Left atria
Apex
How is the anastomoses of the heart relevant to the categorization of the coronary vessels?
Its very sparse
Coronary arteries are therefore deemed functional end arteries (like terminal arteries- not much of collateral supply)
How does blood from coronary supply travel back into the atrium?
Middle, small (right marginal vein), posterior cardiac, anterior interventricular veins -> great cardiac vein will all drain into the coronary sinus on posterior aspect of heart within the atrioventricular groove
The anterior veins of right ventricle will drain directly into the right atrium
Which heart chamber forms most of the base of the heart and receives the pulmonary veins?
Left atrium
Remember the apex is at the bottom!
What venous system drains the intercostal veins?
Azygous vein (drains largely posterior intercostal veins into superior vena cava) Internal thoracic vein (drains breasts and intercostal veins into brachiocephalic vein)
What anatomical points can be found by identifying the location of the sternal angle?
- Marks the point where 2nd costal cartilage articulate with sternum
- At level of T4-T5 intervertebral disc
- The level of the transverse thoracic plane which divides the mediastinum into the superior and inferior mediastinum
- It overlies the aortic arch on the left and the superior vena cava on the right.
- It is roughly at the level of the bifurcation of the trachea and therefore superficial to the carina
- Roughly at the level of the bifurcation of the pulmonary trunk.
- Left recurrent laryngeal (under arch of the aorta)
- Thoracic duct empties into left subclavian vein here
What is the physiological reason for possible splitting of the 2nd heart sound?
During inspiration the pulmonary valve closes later and the aortic valve closes earlier
-due to increased pressure of lung expansion causing slower flow out of right ventricles
What is Virchow’s Nodes?
Lymph node found at the venous angle
Swelling can be indicative of stomach cancer (70%), or breast, lung cancer
What changes in; circulation hormones, autonomic activity, and serum ion concentrations, impact firing rates of the SA node?
AN- sympathetic (tachycardia) and vagal stimulation (bradycardia)
Hormones- Hyperthyroidism (tachycardia) and hypothyroidism (bradycardia). Nor/Adrenaline (tachycardia)
[Ion]- hyperkalaemia (bradycardia) and hypokalaemia (tachycardia) due to impact on repolarization
What is ptosis and what can cause it?
Un-dilated pupil, droopy eye lid, drier face.
Related to a Pancoast tumour (lung cancer), or myasthenia gravis,
How does the vasovagal response relate to syncope?
Thing like fear and/or emotion cause stimulation of vagus nerve, resulting in fainting and slowed heart rate
What is carotid sinus syndrome?
Overactive carotid vagus nerve.
Stimulation of vagus nerve causes fainting, slowed heart rate.
Carotid sinus massage can be used to treat- but very dangerous.
How can you evaluate swallowing capabilities?
Barium swallowing test.
Allows you to visualize liquid moving down oesophagus into stomach using barium which shows up white on an x-ray.
What is the respiratory epithelium and what are exceptions?
Pseudostratified ciliated columnar epithelium cells and goblet cells
Exception: Inferior pharynx has stratified squamous epithelium (protect from abrasion and chemical damage)
How do goblet cells differ as you descend through the respiratory tract?
Less present as the trachea descends.
They become Club cells at respiratory bronchioles, which help produce surfactant
What is the mucociliary escalator?
Self clearing mechanism
Mucous traps particles and creates watery and viscous layers.
Cilia project into watery layer, and they move in synchrony to move mucous away from lungs.
What disease is associated with the mucociliary escalator and how?
Cystic Fibrosis
Chromosomal mutation in chloride channels of cells leads to more viscous mucous, making it difficult to move mucous up the mucociliary escalator
What supports the trachea?
Hyaline C-shaped cartilage
Smooth muscle attaches the edges of the C-shaped cartilage (trachealis muscle)
What layers, beginning in lumen, surround the trachea, and what are found in the layers?
Mucosa- Respiratory epithelium, cilia, goblet cells
Submucosa- Nervous tissue and blood vessels. Rich in seromucous glands (produce watery and mostly mucous secretions, delivered to luminal surface by ducts- aids in humidification)
Cartilage Layer- Hyaline, perichondrium, trachealis muscle
Adventitia- loose connective tissue
Do C-shaped hyaline rings support the entire respiratory tract?
No
At secondary bronchi they become small segmented plates, and stop completely at the bronchioles (more smooth muscles in walls)
What structures help form the bronchioles on a histological level?
No cartilage
No submucosal glands
Largely smooth muscle forming walls
Large bronchioles have simple ciliated columnar epithelium with few goblet cells
Smaller bronchioles have simple cuboidal with few ciliated cells and more club cells
What do Club cells do?
Form surfactant
Also serve as progenitor cells for ciliated/secretory epithelium
What is significant about the terminal bronchioles?
Last part of conduction system, helping move air from bronchioles to respiratory bronchioles
Describe the pneumocytes present in the alveoli.
Type 1 pneumocytes- gas exchange. Flattened squamous cells
Type 2 pneumocytes- produce surfactant to prevent alveolar collapse. Type of progenitor cell that can replenish both 1 and 2 pneumocytes. Account for 60% of cells but cover 5% of surface area.
How many alveoli are in a human lung on average?
500 million
What is the blood-air barrier and what helps to form it?
Prevents blood and air from mixing.
Type 1 pneumocytes and endothelial cells of capillaries, with fused basement membranes
How does lung fibrosis impact the lung on a histological level?
Thickening of lung tissue / blood-air barrier resulting in increased space between t1 pneumocyte and capillary
Creates inefficiency for gas diffusion
What cell type forms the endocardium?
Simple Squamous epithelium which is continuous with the endothelium of blood vessels
What structures/cells are found in the epicardium?
Known as visceral pericardium consisting of;
External simple squamous epithelium (mesothelial cells of mesodermal origin)
Internal areolar tissue (loose connective tissue).
Neutrophils clear dead myocytes (which cant be replaced).
Nerves and vessels supplying the heart are found here in areolar tissue, with lots of adipose surrounding it
What occurs when myocytes die?
Replaced by polymorphs (scar tissue), which can weaken heart.
Myocytes are terminally differentiated
How do Purkinje Fibres appear histologically, and how do they differ from myocytes?
Many mitochondria, paler (due to fewer myofibrils), larger than myocytes, can conduct action potentials more quickly than myocytes .
They radiate into the subendocardium of ventricular walls
What is the subendocardium?
Connective tissue layer within endocardium (below simple squamous epithelium) containing Purkinje Fibres
What is found within the intercalated discs connecting myocytes?
Gap junctions for ion movement
Desmosomes for mechanical connections of myocytes
How do muscular and elastic arteries differ?
Elastic: Numerous bundles of elastic fibres (elastic laminae) in media, deal with high pressures near heart
Muscular: smaller arteries, thick tunica media with lots of smooth muscle and little elastic tissue (helps maintain BP), internal/external elastic laminae on either side of media
How do veins appear in cross-sections- touch on layers and what they are composed of.
Large tunica adventitia
Adventitia is composed of collagen
Thin tunica intima
Relatively thin media with layer of smooth muscle cells
What structures/cells are found in the myocardium?
Cardiomyocytes form thick muscle layer (single, central nucleus, many mitochondria, glycogen rich, y-shaped)
Intercalated discs join cardiomyocytes (formed using gap junctions, desmosomes, and adherens)
