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Muscle and Blood Vessel Histology

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Smooth muscle
Longitudinal
Nucleus
What type of muscle is this?
How has it been cut?
What is the red arrow pointing at?
Smooth muscle
Transverse
What type of muscle is this?
How is it cut?
Connective tissue
What is the layer of lighter pink tissue between the muscle tissue of the muscularis externa?
Nucleus of a smooth muscle cell
Nucleus of a fibroblast
What is the red arrow pointing at?
What is the green arrow pointing at?
ECM
An artefact
This is connective tissue. What fills the white space?
What is this space called on a slide?
Skeletal
Smooth
What type of muscle is in the top right of this image?
What type of muscle is int he bottom left of this muscle?
Transversely cut skeletal muscle cell - Outer longitudinal layer
Longitudinally cut mix of smooth and skeletal muscle - Inner circular layer
Muscularis externa
This is from the upper oesophagus.
What type of muscle is in the left box? And what is this layer called?
What type of muscle is in the right box? And what is this layer called?
What do these layers of muscle make up?
Muscularis mucosae
What is the layer of muscle as indictated by the red box?
The cells have been cut in different places
Y: Through the tip of the cells - tip of nucleus seen
R: Through the middle of the cell - nucleus large
G: Through the cytoplasm of the cell - no nucleus
This is transversely cut muscle. Why do the nuclei of the cells appear different sizes/absent?
How have the cells been cut:
Yellow arrows?
Red arrows?
Green circle?
What is the evidence that supports this?
An intercalated disc
This is from the myocardium.
What is the green arrow pointing at?
It has two nuclei
No branching
This is from the myocardium.
What is different about this cell compared to most other cells?
Does this cell show branching?
Yes - on the left
This is from the myocardium.
Does this cell show branching?
Purkinje Fibre
This is from heart tissue
What is this structure?
An intercalated disc
This is from the myocardium.
What is the arrow pointing at?
An intercalated disc
This is from the myocardium.
What is the arrow pointing at?
The myocardium
The pericardium
The endocardium
What layer of the heart is indicated by:
The green box?
The red box?
What layer in not indicated?
A fascicle of cardiac myocytes
This is from the myocardium.
What structure is this?
The endocardium
This is from the heart.
What is the green arrow pointing at?
Part of a purkinje fibre
This is from the heart.
What is this structure?
A large artery to the heart - a coronary artery
Ignore the red box. This is from the heart.
What is the large structure in the centre of the image?
Tunica intima
This is from an artery. What is layer is the green arrow pointing at?
Tunica media
Tunica adventitia
What layer of the blood vessel is indicated by the:
Left box?
Right box?
The inner elastic lamina (IEL)
Elastic fibres in the media
Muscular - IEL is only present in muscular arteries
What is the green arrow on the left pointing at?
What is the green arrow on the right pointing at?
What type of artery is this? ...Why?
External elastic lamina (EEL)
Muscular - EEL is only present in muscular arteries
What is this structure?
What type of artery is this? ...Why?
Media
Elastic - can see lots of elastin fibres
What layer of the blood vessel is this?
What type of artery is this?
Muscular - can see lots of cell nuclei
This is the media of an artery
What type of artery is is?
Elastin fibres
What fibres are these?
The hepatic portal vein
This is the structure of a particular blood vessel. What blood vessel is it? (Take note of the thick layer indicated by the red BOX)
The hepatic artery
The upper blood vessel indicated by the upper circle is the hepatic portal vein. What is the sturcture indicated by the lower circle?
The hepatic portal vein
The lower blood vessel indicated by the lower circle is the hepatic artery. What is the sturcture indicated by the upper circle?
A submucosal gland
What is this structure?
Elastin fibres
This is from the media of an artery. What are the arrows pointing at?
A nerve
What is this structure?
A nerve
What is the structure indicated by the arrow?
A nerve
What is the structure indicated by the arrow?
A nerve
What is the structure indicated by the arrow?
A nerve
What is the structure indicated by the arrow?
An adipocyte
What is the cell indicated by the arrow?
Connective tissue
What is the tissue indicated by the arrow?
A blood vessel
What is the structure indicated by the arrow?
Muscularis externa
What is the layer indicated by the arrows?
Submucosa
What is the layer indicated by the arrows?
Mucosa
What is the layer indicated by the arrows?
Adventitia
What is the layer indicated by the arrows?
Striated muscle
What is skeletal muscle also known as?
Bones
Where are the usual origins and insertions of muscles?
The heart
What does cardiac muscle form?
Walls of hollow organs
What does smooth muscle form?
GI tract
Respiratory tract
Urogenital tract
Blood vessels
What are examples of the organs that smooth muscle make the wall up of? (4)
Striated muscles that are not skeletal or cardiac
What is visceral striated muscle?
Embryonic derivation
Where are visceral striated muscles derived from?
Head and neck
Where is visceral striated muscle found? (2)
Pharynx
Larynx
Oesophagus
What are examples of structures in which visceral skeletal muscles are found? (3)
Connective tissue element
Services (blood vessels and nerves)
When referring to a tissue, what does the term muscle include?
Contractile protein fibres are organised into alomst crystalline array that refracts light
Why does skeletal muscle look striped?
Muscle fibres
What are striated muscle cells also called?
Length: 1mm to 30cm
Diameter: up to 300microns
What is the average length and width of striated muscle cells?
By associated connective tissue
Muscle cells are not attached cell to cell, how are they mechanically connected?
For storage of Ca2+
Why is the sarcoplasmic reticulum well developed in striated muscle cells?
For the influx of Ca2+
Why is the T-tubule system present in muscle cells?
The cell uses alot of ATP in muscle contraction
Need lots of mitochondria to produce it
Why do muscle cells contain many mitochondria?
In the periphery of the cell
(Around the edge)
Where are all the nuclei located in the muscle cell (which is polynucleate)?
Bundles called myofibrils
How are the contractile proteins of muscle cells arranged?
The sarcomere
What is the contractile unit of a muscle cell?
Many
How many nuclei do striated muscle cells have?
Bundles
Sheets
Bands
How are groups of smooth muscle arranged? (3)
Spindle shaped
What is the shape of a smooth muscle cell?
Fusiform
What is the technical word for spindle shaped?
Through gap junctions
How are smooth muscle cells electrically coupled to one another?
Less
Does smooth muscle contain more or less connective tissue than striated muscle?
Mononucleate
Are smooth muscle cells mononucleate or polynucleate?
The cell has a single nucleus
What does mononucleate mean?
In the centre of the cell
Where is the nucleus of a smooth muscle cell located?
2-10 microns
Usually 5 microns
What is the diameter of a smooth muscle cells?
0.2 mm
10-600 microns
What is the length of smooth muscle cell?
Very developed
How developed is the sarcoplasmic reticulum in the skeletal muscle cells?
Poorly developed
How developed is the sarcoplasmic reticulum in smooth muscle cells?
Plasmalemmal structures
What structures do smooth muscle cells have to utilise to make up for poorly developed sarcoplasmic reticulum?
Caveolae
What are the plasmalemmal structures of smooth muscles called?
Smooth muscle cells
In which of the three types of muscle cells are T-tubules not present?
A branching of cells
What is a syncitium?
Cardiac muscle cells
Which of the three types of muscle levels can form syncitiums?
Through intercalated discs
How are cardiac muscle cells mechanically and electrically joined together?
Desmosomes
Gap junctions
What are intercalated discs made out of? (2)
One - occasionally two
How many nuclei do cardiac muscle cells have?
Centrally
Where are the nuclei located within a cardiac cell?
Terminal cisternae
What does the sarcoplasmic reticulum of cardiac muscle cells lack?
...
What are terminal cisternae?
Cardiac muscle
Which of the three muscle types has the most mitochondria within cells?
...
How are contractile proteins of cardiac muscle arranged?
Sarcomere
Whats is the contractile unit of cardiac muscle cells?
10-20microns
What is the diameter of a cardiac muscle cell?
50-100microns
What is the length of a cardiac muscle cells?
Autonomic nerves
Which nerves innervate smooth muscle?
Very unspecialised
How specialised are autonomic neuromuscular junctions?
Humoral
What other control, other than nervous, are smooth muscle cells under?
Contract without neural stimulation
What can cardiac cells do that other cells cannot?
Pacemaker cells
What is the timing of the contraction of cardiac myocytes controlled by?
Specialised cardiac muscle that determine the pace of cardiac contractions
What are pacemakers cells?
Continuous
Fenestrated
Discontinuous
What are the three types of capillary?
Continuous
What is the most common type of capillary?
Continuous
Which capillary type if the most impermeable?
Gap junctions
How are the endothelial cells of continuous capillaries connected to each other?
A hole
What is a fenestrae?
Capillaries in which the endothelial cells have small pores
What are fenestrated capillaries?
Junctional complexes
How are adjacent cells of fenestrated capillaries connected?
Very permeable
How permeable are fenestrated kidneys?
Bowmans capsule in kidney
GI tract in villi of small intestine
Where are fenestrated capillaries typically found?
In the liver
Where are discontinuous capillaries found?
Hepatic sinusoids
What do discontinuous capillaries form?
Reticular fibres
What are discontinuous capillaries supported by?
Unattached/Unconnected
How may adjacent endothelial cells of discontinuous capillaries appear?
Functional tissue of an organs as distinguished from connective and supporting tissues
What is parenchyma tissue?
Connective tissues
Supporting tissues
What is parenchyma tissue distinguished from? (2)
Almost no barrier
What kind of barriers between the blood and the parenchyma do discontinuous capillaries provide?
The circulatory system
What is the lymphatic system a part of?
The vascular system
What is the lymphatic system not a part of?
Tissues
Lymphatic vessels
Lymph node
Lymphatic vessels
Thoracic lymph node
Vena cava
What is the pathway that lymph takes from tissues to vena cava?
Fat
Protein
Electrolytes
What does lymph contain? (3)
Homeostasis of extracellular space
What is lymph involved in?
Numerous valves
What is the main notable structure of lymphatic vessels?
1-2mmHg
What is the pressure of the lymphatic system?
The pressure is so low, values prevent any back flow as the lymph is moving against gravity to return to the vena cava
Why do lymphatic vessels need valves?
(~) 50 mmHg
What pressures can the lymphatic system rise to during intense muscular activity (e.g. exercise or getting a massage)?
Circulatory system
In what system are all components lined with endothelial cells?
Simple squamous epithelial cells
What are endothelial cells?
Humoral control
(Blood borne factors and secretions)
What are endothelial cells mainly under the control of?
They maintain the potential to divide
Why can endothelial cells regenerate?
Clotting factors
Anti-clotting factors
Vasoconstrictors
Vasodilators
What types of molecules can endothelial cells secrete? (4)
Factor VIII
Give an example of a clotting factor secreted by an endothelial cells?
Prostacyclin
Give an example of an anticlotting factor secreted by an endothelial cell?
...
Give an example of a vasoconstrictor molecule secreted by an endothelial cell?
NO
ATP
Give an example of a vasodilator molecule secreted by an endothelial cell? 92)
Conductance/distributing vessels
What are the main types of blood vessels?
Arterioles
What is the main resistance vessel?
Peripheral resistance
What are arterioles major contributors to?
Blood pressure
Because arterioles are contributors to peripheral resistance, what do they also indirectly contribute to?
Capillaries
Post-capillary venules
Small venules
Name three different exchange vessels?
Exchange of nutrients, gases and metabolites with the tissue
What are the exchange vessels main function?
Veins
Shunt vessels
What are the two main conductance vessels?
...
What are shunt vessels?
Arterio-venous anastomoses
What does AVA stand for?
In short circuit capillary beds
Where are AVAs and metarterioles found?
Control perfusion through capillary beds
What do AVAs and metarterioles do?
Tunica intima
Tunica media
Tunica adventitia
What are the three main layers of blood vessels?
The innermost layer of the vessel
What is the tunica intima of a blood vessel?
Endothelial cells
Connective tissue
What are the components of tunica intima? (20
The middle layers of blood vessels
What is the tunica media of a blood vessel?
Smooth muscle
Connective tissue
What are the components of tunica media? (2)
The outermost layer of vessels
What is the tunica adventitia of a blood vessel?
Connective tissue
Services
What are the components of tunica adventitia? (2)
Media and adventitia
Or just adventitia
What components of blood vessels may be absent from smaller vessels?
Intima is avascular
What characteristic of the intima is not a characteristic of the media or adventitia?
From other vessels
(Vaso vasorum)
Where do the media and adventitia of large blood vessels get their blood supply?
Vessels of the vessels
What does vaso vasorum mean?
Aorta
Brachiocephalic
Common carotid
Subclavian
Pulmonary
Give examples of large elastic arteries. (5)
Endothelium
Thin layer of connective tissue
Some collagen
Few elastic fibres
What are the components of the intima of large elastic arteries? (4)
Thick spiral of smooth muscle
Muscle interweaved with sheets of elastic fibres
Collagen fibres
What are the components of the media of large elastic arteries? (3)
Thick connective tissue
Collagen
Vaso Vasorum
Nerves
What are the components of the adventitia of large elastic arteries? (4)
Large muscular arteries
What type of artery are the majority of systemic arteries classed as?
Endothelium
Layer of connective tissue
Inner elastic lamina
What are the components of the intima in large muscular arteries? (3)
Inner elastic lamina
What does IEL stand for?
Elastic fibres
Some collagen fibres
What comprises IEL? (2)
A thin layer
What is a lamina?
Thick spiral of smooth muscle
Little connective tissue (little collagen, a few elastic fibres)
What are the components of the media in large muscular arteries? (2)
Thick connective tissue
External elastic lamina
Collagen
Blood vessels
Nerves
What are the components of the adventitia in large muscular arteries? (5)
External elastic lamina
What does EEL stand for?
Endothelial cells
(No IEL)
What are the components of the intima in arterioles? (1)
Smooth muscle
What are the components of the media of arterioles? (1)
3-6 cells thick
How thick is the layer of smooth muscle that makes up the tunica media of an arteriole? (Size in terms of cells)
Merges with the surrounding connective tissue
What is different about the adventitia of arterioles?
Tunica intima only
(No media or adventitia)
What are the components of capillaries and post-capillary venules?
Endothelium
What are the components of the intima of capillaries? (1)
Endothelium
What are the components of the intima of post-capillary venules? (1)
Pericytes
What are the endothelial cells of the capillaries and post-capillary venules surrounded by?
Elongated connective tissue cell found wrapped around capillaries and small blood vessels
What are pericytes?
Adventitial cells
What are pericytes also known as?
Endothelial cells
What ar the components of the intima of venules and veins? (1)
Smooth muscle
What are the components of the media in venules and veins? (1)
2+
How many cells thick is the tunica media of veins
1-2
How many cells thick in the tunica media of venules?
Often absent or indistict
What is different about the tunica adventitia of veins and venules?
>2mm
What diameter will a vei have before it needs valves?
2 leafs of connective tissue covered in endothelial cells
What are valves?
Collagen fibres
What type fo connective tissue is found in valves?
Renal veins
What is an example of a large muscular vein?
Elastic fibres may be present
What is different about the media and adventitia of large muscular veins compared with normal veins?
Has other longitudinal muscle and inner circular muscle
What is different about the media of the hepatic portal vein compared to normal veins?
(~) 6 cells each
How many cells thick is each layer of extra muscle in the tunic media of the hepatic portal vein?
Blood has been through GI tract capillaries
So is at a lower pressure
Vein needs extra muscle to pump blood up to the liver
Why does the hepatic portal veins have extra muscle?
Endothelial cells
Reticular fibres
What are the components of the intima of lymphatic vessels? (2)
Thin layer of smooth muscle
(sometimes it isn't present
What are the components of the media of lymphatic vessels? (1)
1 cell thick
How many cells thick is the layer of smooth muscle found in the tunica media of lymphatic vessels?
Autonomic nerves
What are all blood vessels innervated by?
Sympathetic innervation
What is the most common innervation of the blood vessels?
Vasodilation
What does parasympathetic innervation of the blood vessels mediate?
para vascular nerves
What are blood vessels often accompanied by?
Sympathetic
Parasympathetic
Somatomotor
Sensory
What neurones do para vascular nerves contain? (4)
Other target organs other than blood vessels
Where are para vascular nerves travelling to?
Media
or Media/Adventitia border
Where does innervation of blood vessels tend to be confined to?
Permeability of the blood vessel
What are nerves associated with capillaries likely to control?
Enlarged areas of the sarcoplasmic reticulum surrounding the t-tubules
What are terminal cisternae?
Control the number of impulses being sent to myocytes
So control the pace of heart contractions
What do pacemaker cells of the heart do?
Fibroblasts:
-Pointyften
-Often curved, bent, wavy
-Slim
Smooth muscle:
-Not pointy
-Not curved, bent, wavy
-Plump
What are the differences between fibroblast nuclei and smooth muscle nuclei?
Gap junctions
What type of junction is found between smooth muscle cells?
In the oesophagus
What is the only where striated and smooth muscle intermingle?
Small
Usually one nuclei
Central nucleus
Joined by specialised junctions
What are the similarities between cardiac muscle cells and smooth muscle cells? (4)
Gap junctions
Adherens junctions
What types of junction are found between cardiac muscle cells? (2)
To allow electrical conductivity between cells
To allow the propagation of action potentials through the myocardium
What is the function of gap junctions between cardiac muscle cells? ...Why is this function important?
Through gap junctions as ions
How is electrical activity passed between cardiac cells?
To physically connect the cells
What is the function of adherens junctions between cardiac muscle cells?
Striated
Similar arrangements of contractile filaments
Similar t-tubules
Similar sarcoplasmic reticulum
What are the similarities between cardiac muscle cells and skeletal muscle cells? (4)
Specialised smooth endoplasmic reticulum
What type of reticulum is sarcoplasmic reticulum?
Single cells can be branched
Innervated by purkinje fibres
Single cells occasionally have two nuclei
What are the features of cardiac muscle that are not found in any other type of muscle cell? (3)
A bundle of structures
What is a fascicle?
A bundle of cardiac myocytes
What is a fascicle of cardiac cells?
Muscular
In what type of artery is an IEL and EEL found in?
Elastic
What type of artery are IEL and EEL not found in?