Spinal Nerves and Heart

ANS/ Visceral Efferent

Involuntary control of body

At least 2 neuron systems

Sympathetic and Parasympathetic systems

Preganglionic

Cell body in CNS

Axon exits CNS

Synapses to the postganglionic neuron in a ganglion

Postganglionic

Cell body in ganglion

Axon goes to smooth/cardiac muscle or glands

Sympathetic

Fight or Flight

• Used if actively hunting, running…

Parasympathetic

Rest and Digest

• Used if sleeping, eating, GI motility

Sympathetic Trunk

From communicating branch of spinal nerves

Postganglionic cell bodies

Sympathetic Nervous System

Preganglionic neurons:

• Cell bodies in thoracolumbar region (T1-L5)

Post ganglionic neurons:

• Cell bodies in visible ganglia

“Thoracolumbar” system

Preganglionic fiber→ synapse at ganglia→ post ganglionic fiber

Cervical Ganglia - Sympathetic

3. Cervicothoracic ganglion- ganglion close to sympathetic trunk

4. Ansa subclavia- connects cervicothoracic/middle cervical ganglia

   • Forms ring around subclavian aa

25. Middle cervical ganglia

    • Vagosympathetic trunk (29) passes through (does not synapse)

    • Cranial nerves to heart (22)

Abdominal nerves

Preganglionic fibers from sympathetic trunk

11. Major splanchnic n

14. Minor splanchnic n

17. Lumbar splanchnic n

34. Celiacomesenteric ganglion

    • to abdominal viscera

23. Caudal mesenteric ganglion

Parasympathetic Nervous System

Preganglionic neurons in cranial/sacral region - “craniosacral” system

Postganglionic neurons found on their target structures- not visible ganglia

*If tagged on a parasympathetic nerve, it will always be preganglionic nerve fibers

Vagus Nerve (Cranial Nerve X)

Vagus- Esophagus

Originates in medulla

3 types of nerve fibers:

Visceral sensory fibers, somatic motor fibers, and visceral motor/ parasympathetic fibers.

Visceral sensory (Vagus) nerve fibers

sends information from pharynx, larynx, trachea, esophagus, and thoracic/ abdominal viscera

Somatic motor (Vagus) nerve fibers

innervates larynx, pharynx, esophagus

Visceral motor/ parasymapthetic nerve fibers

to thoracic and abdominal organs

*preganglionic/presynaptic parasympathetic fibers

Damage to Vagus nerve

decreased gut motility

Vagus nerve

starts out as part of Vagosympathetic trunk (in carotid sheath)

Gives off recurrent laryngeal nerves

R & L recurrent laryngeal nn.

Right recurrent laryngeal n

wraps around R subclavian a

Left recurrent laryngeal n

wraps around Aortic arch/ ligamentum arteriosum

• longer, more likely to get damaged- Laryngeal hemiplegia (Roarers)

Vagus nerve- more branching

Caudal to heart, divide into dorsal and ventral branches

Both vagal trunk go through esophageal hiatus

L/R ventral vagal branches

combine to make ventral vagal trunk more cranially

L/R dorsal vagal branches

combine to make dorsal vagal trunk more caudally

Heart position

The base of heart is actually the “top”

• points dorsocranially

The apex of heart points ventrocaudally.

Heart spans intercoastal spaces 3-6 in a dog

• angled roughly 45 degrees

Apex of heart

points ventrocaudally

made of left ventricle

Auricular surface

Left side of heart- faces left side of chest

“Auricular” because you can see both auricles or “ears”

What is number 1?

Left auricle

What is number 2?

Pulmonary trunk

What is number 3?

Right ventricle

What is the highlighted portion near number 3?

Conus Arteriosus

What is number 4?

Left ventricle (apex)

What is number 5?

Right auricle

Atrial surface

Right side of heart - right side of chest

“Atrial” because you can see right atrium really well

What is number 1?

Right atrium

What is the portion in highlighted in magenta?

Sinus venarum

Sinus verarum

The sinus is a space, venarum refers to veins

space where cranial and caudal vena cavae drain into

What is number 2?

Caudal vena cava

What is green?

Cranial vena cava

What is in blue?

Aorta

What is outlined in pink?

Right ventricle

Flow of Blood

Crainial and Caudal vena cavae drain blood into right atrium → Right atrium through right atrioventricular valve/ Tricuspid valve → Into right ventricle → right ventricle through pulmonary valve/a semilunar valve → pulmonary arteries to lungs→ Pulmonary veins from lungs into left atrium → Left atrium throught left AV valve/mitral valve into left ventricle→ left ventricle through aortic valve/semilunar valve into Aorta → Aorta → aortic arch → body

Pulmonary circulation

blood to lungs - pulmonary trunk

Systemic circulation

blood to body - aorta

Systole

ventricles contracting - blood ejected into either pulmonary or systemic circulation

Diastole

ventricles relaxing and atria contracting - blood filling ventricles

First heart sound (lubb/systole)

closure of two AV valves (tricuspid/ mitral)

• blood hitting valves, closing AV valves - tricuspid (R) and mitral (L)

Second heart sound (dubb/diastole)

closure of semilunar valves (pulmonary/aortic)

• blood closing semilunar valves- pulmonary (R) and aortic (L)

Valve projection - left side

Valve: P A M

Intercostal space: 3 4 5

Valve projection - right side

Valve: T

Intercostal space: 4

What is outlined in green?

Visceral pericardium/ epicardium

• on heart, can’t get off

What is outlined in purple?

Parietal pericardium

What is outline in tan?

Fibrous pericardium

Fibrous pericardium

Made of endothoracic fascia (“glue”)

Connects parietal pericardium and pericardial pleura

What is outlined in orange?

Mediastinal/pericardial pleura

What is in blue?

Phrenicopericardial ligament

Phrenicopericardial ligament

connects diaphragm and pericardium

What is outlined in orange?

Pericardial/ Mediastinal Pleura

What layer is in grey?

Fibrous pericardium - endothoracic fascia

What is outlined in purple?

Parietal pericardium

What is outlined in green?

Epicardium/ visceral pericardium

What layer is in pink?

Myocardium - heart muscle

What is highlighted in yellow?

Endocardium - inner lining of heart muscle

Fibrous base

“Cardiac Skeleton”

• 4 fibrous rings for valves to attach to

• Separates atrial mass from the ventricles

Sinoatrial nodes

pacemaker, in right atrial wall

Atrioventricular node

in interatrial septum

Atrioventricular bundle

R/L bundles straddle interventricular septum

Right Atrium

Intravenous tubercle

Fossa ovalis

Coronary sinus

Pectinate muscles

RIGHT atrioventricular valve/tricuspid valve

What is the structure in blue?

Intravenous tubercle

What is the structure in red?

Fossa ovalis

What is the structure in pink ?

Coronary sinus

What is the structure in purple?

Pectinate muscles

Intervenous tubercle

tubercle between where two vena cavae dump blood

*only in right atrium

Fossa ovalis

closed foramen ovale between where blood was shunted between right and left atria in fetus

• thin indentation

Coronary sinus

hole where dirty blood from heart is returned to right atrium

Pectinate muscles

ridges in auricles

Right ventricle

Papillary muscles

Chordae tendinae

Trabeculae septomarginalis

Trabeculae carnae

Pulmonary valve - semilunar valve, leading to pulmonary trunk

What structure is in pink?

Papillary muscles

Papillary muscles

what chordae tendinae attach to

What structure is in green?

Chordae tendinae

Chordae tendinae

attach to valves

What structure is in blue?

Trabeculae septomarginalis

Trabeculae septomarginalis

nerves

cords from septum to marginal wall

Do NOT attach papillary muscles/valves

What is the structure in orange?

Trabeculae carnae

Trabeculae carnae

meat ridges

Conus arteriosus

funnel shaped part of right ventricle, leading into the pulmonary trunk

Pulmonary valve

semilunar valve

3 cusps, no sinuses

prevents backflow from pulmonary trunk into right ventricle during diastole

Left atrium

less complex than right

multiple openings from multiple pulmonary veins

Has an auricle

Left atrioventricular valve aka Mitral valve

Blood into left ventricle after

The purple arrows show:

Mitral valve

The pink arrows show?

Papillary muscles

What is the tagged structure?

Pectinate muscle

Left Ventricle

Very similar to right ventricle

Thicker - needs to send blood to entire body

Apex of heart

Contains: papillary muscles with chordae tendinae, trabeculae carnae, trabecula septomarginalis

Blood through aortic valve and into aorta after

What is the structures in green?

Chordae tendinae

What are the structures in pink?

Papillary muscles

What are the structures in blue?

Trabecula septomarginalis

What are the structures in orange?

Trabeculae carnae

Aortic valve

Semilunar

3 cusps

2 of the cusps have Aortic sinuses

• Origins of the R/L coronary arteries

  • Supply myocardium with nutritional blood

Heart Grooves

Coronary groove

Paraconal interventricular groove

Subsinuosal interventricular groove

Coronary Groove

separates atria and ventricles

Paraconal interventricular groove

groove next to conus arteriosus

contains paraconal interventricular branch of L coronary a

Subsinousal interventricular groove

groove on the other side

contains subsinuosal interventricular branch of L coronary a.

Coronary arteries

Supply myocardium with nutritional blood

Right coronary a

Left coronary a

• Paraconal interventricular branch

• circumflex branch (in coronary groove)

• Subsinousal interventricular branch

Right coronary artery

no major branches

Runs in coronary groove