Imaging: Histology of the Heart Flashcards
What is the difference between a myocyte vs. a myofiber?
- A myocyte is a single muscle cell while a myofiber is composed of a series of myocytes aligned end-to-end to produce a directionally-uniform contractile force (more-or-less).
- In the case of skeletal muscle myofibers, the multiple myocytes fused to form a single myofiber.
- But with cardiac and smooth muscles, the myocytes remain distinct and require intracellular adhesions to transmit forces throughout the myofiber.
409: This is the wall of the artery exiting the heart. In this section, the artery has been cut longitudinally, thus it appears much different, compared to specimens that are cut in cross-section (transversely).
* Would this artery be classified as elastic, muscular, or arteriole? Explain your rational?
410: Which tissue layer would form the lining of this artery’s lumen?
409: Elastic; very thick tunica media with elastic lamellae interspersed between smooth muscle fibers (>40 layers)
410: endothelium
Define the following terms and their function, as they relate to cardiac muscles
Dyad
The combination of a T-tuble and a single cistern of the SR (skeletal muscles possess a triad — a T-tubule and two SR cisterns, one on each side); their interaction ultimately leads to an increase in cytosolic Ca2+ levels.
203: Which layer of the atrial wall is indicated by this line? Which tissue comprises the majority of this layer and what is its function?
At what angle are the cardiac myocytes seen here cut? Explain your rational.
Transversly: Cells have a more circular shape; striations and intercalated discs can’t be observed
Semilunar Valve
405: Within this location, the intermingling of the fibrous CT of the cardiac skeleton and muscular tissue of the myocardium can be observed. Name the three major functions of the cardiac skeleton.
- Electrical insulation between the atria and ventricles
- Support of the valves
- Attachment of the myofibers of the myocardium
Define the following terms and their function, as they relate to cardiac muscles
Sarcomere
The functional contractile units of cardiac (and skeletal) myofibrils; consists of the contractile thin and thick filaments located between two Z-discs.
Heart, semilunar valve
411: What tissue is located is indicated here?
* Which layer of the heart would this tissue belong to?
Adipose tissue
- Epicardium
212: This large projection is a pectinate muscle that is a structure found in the atrium proper. What additional feature would indicate that this slide specimen is from the atrial wall and not the ventricular wall
The wall is relatively thin
Define the following terms and their function, as they relate to cardiac muscles
Sarcoplasmic reticulum
The smooth endoplasmic reticulum (sER) of muscle cells; serves as a reservoir of Ca2+ to keep the cytosolic levels low until stimulated to release.
205: The nucleus seen here belongs to which type of cell? How would you classify this epithelial tissue?
* Name two functions of this tissue layer.
303: What is the name for this indicated layer?
Subendocardium
201: This is the endocardium of the atrial wall. Note that the thickness of the layer is not uniform across the entire wall. Which space does this layer face?
* Name the sublayers that make up this layer.
- Lumen of the atrium
- Endothelium
Fibroelastic layer
Subendocardium
304: What is the name for the structure indicated? What type of tissue is it?
* What is the function of this tissue?
Purkinje fiber (or conducting system of heart)
- Conduction of electrical signals to coordinate ventricular contraction
- Which type of muscle tissue is this?
- What are two histological characteristics that are unique to these muscles cells that distinguish them from the other two muscle tissue types?
- Cardiac
- Myocytes are short and blunt.
Some myocytes are branched
Intercalated discs are present
Which side of the heart has a thicker ventricular wall? Why?
Left; systemic circulation requires greater force to generate the pressure needed to drive the blood through the much larger and extensive vascular network.
301: Which tissue is identified by the arrow?
* To which layer of the ventricle wall does it belong?
Endothelium
- Endocardium
206: Identify the cells seen here.
Adipocytes
Define the following terms and their function, as they relate to cardiac muscles
Intercalated disc
The region of attachment between cardiac myocytes composed of multiple junctional complexes that join and electrically-couple the myocytes to assist in effective force transmission and contractile coordination/synchronization.
204: Which layer of the atrial wall is indicated by the this line? Which tissue comprises the majority of this layer and what is its function?
* Which space does this layer face?
305: Which space is this? In a living adult, what would normally occupy this space?
Lumen of the ventricle
- blood
What is the difference between a myofiber vs. a myofibril?
- A myofibril is a bundle of the contractile filaments (thin and thick) organized within the skeletal and cardiac myocytes/myofibers into longitudinal strands.
- They are composed of the contractile proteins (actin and myosin) and their associated proteins that regulate their interactions (tropomyosin, troponin, etc).
Which side of the heart is involved with the adult pulmonary circulation?
Right Side
* Define the following terms and their function, as they relate to cardiac muscles
Sarcolemma
- The cell membrane of muscle cells; contains various ion channels and receptors that respond to neurotransmitters and hormones, which ultimately changes in ion channel permeability, intracellular levels of second messengers and/or enzyme activity.
- In cardiac myocytes, the overall effect includes changes in heart rate and/or contractility.
202: The nucleus seen here belongs to which type of cell? How would you classify this epithelial tissue?
* Name two functions of this tissue layer.
307: What specific tissue is indicated here?
* Why do these cells stain lighter than the contractile cardiac myocytes?
Purkinje fiber (or conducting system of heart), which is a specialized cardiac muscle tissue
- Cells contain fewer myofibrils and contain more glycogen
302 This layer is composed primarily of which types of CT fibers
Collagen and elastic
- Note the presence of smooth muscle cells scattered though out this layer.
