9.4 - Lab + Lecture Notes Flashcards
Elastic Arteries
- designed to buffer pressure difference between systole and diastole
- some of the largest one include:
Brachiocephalic
Common carotid
Subclavian
Elastic Lamina
= layers of fenestrated sheets of elastic fibers + smooth muscle cells
Lamellar unit
- one layer of smooth muscle and its adjacent elastic unit
Tunica Intima
= apical to 1st elastic lamellae
= endothelium + thin layer of CT
Tunica Adventitia
= external layer up to first visible elastic lamina
Muscular Arteries
= most of large arteries that supply major organs
- lamellar units of tunica media are replaced with continuous layers of smooth muscle
- in large arteries the innermost elastic lamina (IEM) and outer most elastic lamina (EEM) is retained
FXN:
- control distribution of blood as it branches
Vasa Vasorum
- carry blood to/from walls of large vessels
Nervi Vascularis
- nerve fibers that innervate smooth muscle of the vessels
Arterioles
- tunica intima = mostly endothelial cells
= smallest branches of arterial system - have smooth muscle in walls (1-2 layers) in the tunica media
Morphology of Capillaries
- have a lumen the size of a single RBC
Venules
- only thing small that is also larger than RBC
- smallest venules have no tunica media
Continuous Capillaries
- in brain or skeletal muscle
Fenestrated capillaries
- found in intestines or endocrine organs
Sinusoidal Capillaries
- larger in diameter
- inference by position within organ
- morphologically indistinguishable from venues in standard preparations
Lymphatic vessels
- consists only of endothelium and small amount of subjacent CT
Valves will be located in, and function to
- will be seen in lymph and larger veins
- function to prevent back flow of blood in low pressure vessels
Function and examples of some of the largest veins
Function: - buffering changes in blood volume - reduce lumenal volume by constricting along length (using longitudinally arranged smooth muscle in tunica adventitia) Examples: Vena Cava Portal vein
Explain how pulmonary circulation differs from systemic circulation
- pulmonary arteries carry deoxygenated blood
- pulmonary veins carry oxygenated blood
- arteries and veins don’t run together
- is a low pressure system - results in slightly different wall structure
Describe modifications that occur to the systemic circulation’s typically flow
- the Portal system
- is where one capillary bed is linked to another capillary bed through and artery or vein
- occurs in renal, digestive, and pituitary gland
Describe the basic 3 layers of the cardiovascular system from outside to inside
1) Epicardium = outer layer - has subepicardium, an extra layer of CT
2) Myocardium = middle layer
3) endocardium = inner layer - has subendocardium, an extra layer of CT
Describe the 3 layers of vessel walls from outside to inside
1) Tunica adventitia - outer - CT
2) Tunica Media = middle - smooth muscle
- is the most modified layer based on FXN
3) Tunica Intima = inner layer - endothelium + subjacent CT
What is the earliest stage that cardiac cells are predetermined in the developing embryo. And what is the location and name of the area they are found in?
- in the 3 layered disc stage
- cardiac cells are predetermined and are localized adjacent to primitive streak
- they migrate to above the oropharengeal membrane - to area called cardiogenic area and form the cardiac crest
Describe the early embryonic formation of the heart
- heart begins to form bilateral cardiac progenitor cells located in splanchnic lateral plate mesoderm
- 2 endothelial heart tubes form with blood islands
- cells from into bilateral heart tubes that fuse during folding and become positioned below oropharengeal membrane with head folding
- after fusion the straight heart tube hangs in pericardial cavity and becomes divided into 3 layers (endocaridum, myocardium, epicardium)
How is the straight cardiac tube initially anchored
@ the cranial end (arterial end) - it is attached t pharyngeal arches
@ caudal end (atrial/venous end) - it is embedded in the transverse septum
What are the key points of the development of the cardiac system
- primordial heart is formed entirely of splanchnic LPM
- lateral folding fuses initially bilateral structures to a single midline line tube with central lumen through which blood flows
- head fold positions heart and pericardial cavity below the oropharengeal membrane + ventral to the gut tube
- heart will form 5 dilations and bend to the right (4/5 will undergo septation)
- cardiac anomalies result from defects in septation
A what day does the continual elongation of the heart form a series of 5 dilations and what are they? (list caudally to cranially)
- around day 22 these structures are formed through a series of dilations (also listed in order of blood flow direction)
1) Sinus Venosus
2) Primitive Antrium
3) Primitive Ventricle
4) Bulbus cordis (conus cordis)
5) Truncous Arteriosus
Describe the Sinus Venosus
- consists of Left and right sinus horns that initially receives 3 paired veins
- location of where the umbilical vein drains as well
Describe the adult structure formed from primitive atrium
- forms the trabecualted RA and all of the LA
- the primitive ventricle and atria are separated by a single atrioventricular canal
Describe the adult structure formed from the primitive ventricle
- forms the LV
- the primitive ventricle and atria are separated by a single atrioventricular canal
Describe the adult structures formed from the Bulbus cordis (conus cordis)
- Proximal = RV
- Distal (conus cordis) = smooth part of walls of RV and LV
Describe the adult structures formed from the Truncous Arteriosus
- proixmal ascending aorta
- pulmonary trunk
Describe the process of cardiac looping
- the primordial heart is anchored at the cranial end by aortic sac and at the caudal end by transverse septum (future diaphragm)
- differential growth of the bulbus cordis and primitive ventricle along with the anchoring causes the heart to bend on itself
- proximal bulbus cordis is displaced caudally, ventrally and to the right
- primitive ventricle is displaced to left
- primitive atrium is displaced dorsally and cranially
Give a brief summary of what occurs during the cardiac looping
Cephalic portion moves: ventral + caudal + right
Caudal Potion moves: dorsal + cranial + left
At the end of cardiac looping what occurs?
- next, the primordial atrium forms two large dilations (corresponding to primitive RA and LA?) and the distal region of the bulbs cordis (conus cordis + truncous arterioles) - shifts to the midline
- this sets the stage for septation of the heart which will forms the definitive chambers + arterial trunks
What are the locations of the 4 septa (walls) that will form and why do they form
- they form to partition the heart to give rise to the definitive structure –> the partitioning is important for unidirectional flow and separation of oxygenated and deoxygenated blood
- the 4 walls that will form are in the:
1) Atrioventricular canal
2) Primitive Atrium
3) Outflow Tract
4) Primitive Ventricle
Describe the organization of tissues surrounding the heart (6 term - from interior to exterior)
1) heart
2) visceral layer of serous pericardium = epicardium
3) pericardial space = pericardial cavity - a potential space containing a thin layer of serous fluid
4) Parietal layer of serous pericardium - lines the fibrous pericardium to form pericardium - sometimes called pericardial sac
5) Fibrous Pericardium = dense CT lying on mesothelium
6) Pleural cavity + lung
What is cardiac tamponade
= excess fluid in pericardial cavity
- life-threatening disease
- caused by blunt trauma, pericarditis, myocardial rupture
Describe the wall of the heart (exterior to interior)
1) Epicardium = visceral layer of serous pericardium - single layer of mesothelial cells
+ subepicardial layer = loose CT with veins, artieries, nerves
2) Myocardium - cardiac myocytes
3) Endocardium = lines lumen of heart - inner layer of endothelium
+ Subendocardial layer = continuous with myocardium (connects CT of endocardium to myocardium)
- contains the conducting position of the heart (location of majority of Purkinje Fibers)
Describe the overall structure of vessel walls (interior to exterior)
- graded change in individual structure (not abrupt changes) as change from elastic –> muscular arteries –> arterioles
- vasa vasorum + vasomotor nerves provide nourishment to the layers
1) Tunica Intimia = endothelium (cells are longitudinal - parallel to direction of blood flow) + CT
2) Tunica media = concentric smooth muscle cells (primarily) with variable amounts of elastic fibers
3) Tunica Adventitia = CT of type I collage + elastic fibers
Describe characteristics of elastic arteries with attention to the tunica media and tunica adventitia
= closest to heart, conducting arteries that allow for dissension during systole - limited by collagen fibers in the TM and TA
- recoil during dystole allows strong blood flow to continue
Tunica Media contains:
- elastin in fenestrated sheets (lamellae), smooth muscle cells, reticular fibers, GS, elastic fibers
Tunica Adventitia contains:
- collagen fibers, elastic fibers (not sheets), fibroblasts, vasa vasorum, nervi vascularis
Describe characteristics of muscular arteries with attention to the tunica media
= distributing arteries, control blood flow to tissues by contracting/relaxing the smooth muscle
- have Prominent IEM
- have some elastic fibers, reticular fibers, GS present
- EEM is present only in larger vessels
Tunica media contains:
- up to 40 layers of smooth muscle cells
- has more smooth muscle cells than elastic fibers as it moves further from heart
Describe characteristics of arterioles with attention to tunica media and tunica adventitia
= regulated vessels + resistance vessels
- smaller than muscular artery
- prominent IEM (usually stains as a pale area)
- arterioles change diameter based on local conditions to regulate flow into capillary beds
- poorly defined tunica adventitia
Tunica Media contains:
- 1-3 smooth muscle layers
Describe characteristics of Capillaries
= the location of the primary function of the cardiovascular system
- very thin walls allow for diffusion
- diameter is usually only large enough to allow 1 RBC to pass at a time (<10microns)
- only consists of endothelial cells + their own BM
- Identify them by looking at the wall first and then size
- 3 types of capillaries
1) Continuous
2) Fenestrated
3) Discontinuous (sinusoidal capillaries, sinusoids)
Describe characteristics of continuous capillaries including FXN and Locations
- Endothelium forms a complete tube to control what crosses its wall
- endothelial cells are joined by tight junctions
- regulated exchange - characterized by the distinct continuity of these capillary endothelial cells
= the most common type of capillary
Locations: - Muscle
- CT
- Exocrine glands
- Nervous tissue
- IN a specialized form in lung + placenta
What are pericytes?
- cells found along capillaries and in post-capillary venues
= mesenchymal cells with long cytoplasmic processes - are enclosed in their own basal lamina that is continuous with the basal lamina of the endothelial walls
- support and contractile cells offering structure and stability
- play key role in development in growth of new vessels and may function in repair of vessels
Describe characteristics of fenestrated capillaries including FXN and Locations
- small circular fenestrae allow for more extensive molecular exchanges
- each fenestrae is covered (usually) by a thin diaphragm containing heparan proteoglycans
- have a continuous basal lamina
Locations: - areas where rapid exchange i needed
- endocrine glands
- intestine
- kidney
Describe characteristics of discontinuous capillaries including FXN and Locations and alternate names
= sinusoidal capillaries = sinusoids
- large, flat, irregular shaped with fenestrations (usually) and gaps
- allow free exchange between blood and interstitial fluid
- blood moves slowly through them allowing for maximal exchange
Location:
- bone marrow
- spleen
- liver (has both fenestrations and gaps)
Describe capillary beds and their regulation of blood flow
= new work that interconnects arterioles and venule (not all blood runs through the network through)
- arterioles first branch into smaller vessels = met arterioles
- metarterioles - have bands of smooth muscle cells on them that form precapillary sphincters - control how much blood enters the capillary bed
- relaxation of precapillary sphincters allows blood to enter bed
- the distal portion of the metarteriole is called the thoroughfare channel
Describe the general characteristics of venous vessels
- return low-oxygenated blood (gives it blue appearance) from capillary bed to right side of heart (exceptions = pulmonary veins and umbilical veins)
- lower pressure in venous system - have thinner walls compared to companion arteries
- veins donts pulse like arteries, are more abundant, have larger diameter, and 80% of BV is stored in them due to expansion capabilities and diameter
- characterized by very large lumens and very thin walls - where adventitia is the majority of the wall
- many have valves = foldings of TI into lumen
What are the 3 types of venules
1) Immediate post-capillar venules
2) Muscular venules
3) High endothelial venule (HEV)
Describe immediate post-capillary venules
- structurally similar to capillaries
- participate in exchanges between blood and tissue
- primary site of WBCs exiting circulation
Describe Muscular venules
- as increase in size from post-capillary to muscular and up –> the tunica media starts to have recognizable smooth muscle
Describe high endothelial venules (HEV) and their common locations
= specialization of venules
- cuboidal shaped epithelium (not squamous)
- facilitates rapid migration of lymphocytes into lymphoid tissue
- l-slectin in lymphocytes recognzies ligand on endothelial cell surface and integrins promote adhesion allowing them to cross the walls
- recognize them by the lumen, blood, lymphocytes
FXN:
- lymphocyte migration from systemic circulation into the tissue
Location:
- lymph node, tonsils, Peyer’s patches of small intestine
Describe the characteristics of veins and how blood flow is carried out in them:
- thin tunica media + tunica adventitia that is well developed
- blood flows under low-pressure moving due to:
A) Tunica Media Contraction
B) external compression of muscles and organs - vein valves project from tunica intima
- valves are made by semilunar folds of TI (elastic fibers and endothelium)
- not all veins have valves - but most numerous in legs
Describe characteristics of special large veins such as inferior/superior vena cava and how to recognize them
- largest layer = tunica adventitia
- tunica adventitia contains longitudinal arranged bundles of smooth muscle
HINT on practical exam:
++ this will look like digestive system/wall of intestine –> determine endothelium to eliminate possibility of digestive system
Describe the lymphoid system
= “overflow system”
- drains surplus tissue fluid
- removes cellular debris
- monitors for infection/pathogens
- all parts lined with endothelium
- begins in CT as blind-ended system of vessels –> carries lymph in progressively larger vessels that fuse and eventually empty in large veins near heart
Describe the lymphatic capillaries
= unidirection blind-ended vessels in capillary beds
- consist of single layer of endothelium (no tight junctions) and an incomplete BM
- held open by anchoring filaments of elastin covered in endothelium that bind the vessels to surrounding CT
Describe lymphatic vessels
= formed by merger of lymphatic capillaries
- walls remain very thin
- usually do not contain RCBs
- have an abundance of valves –> large vessels appear beaded due to number of valves
- merger of lymphatic vessels gives rise to lymphatic trunks forming right lymphatic duct and thoracic duct
What is lymph?
= clear fluid in lymph system
- have similar composition to blood plasma
- is filtered by lymph nodes
what are Lymph Nodes?
= encapsulated structures containing elements of body’s defense system
- certain body areas are known for the abundance of them
- function in filtration of the lymph
What is the right lymphatic duct?
- is the larger lymph vessel that empties into a large vein near the right atrium of the heart
- its function is to drain the upper right body quadrant
What is the thoracic duct?
= larger lymph vessel that empties into a large vein near the right atrium of the heart
- can be seen in gross anatomy
- drains all of body not drained by right lymphatic duct (everything but the upper right quadrant
