Exam 1 Flashcards
When cut in cross section and viewed with a transmission electron microscope (TEM), basement membranes have a characteristic 3 layered structure. Name these layers and describe the appearance of the image.
- the top layer is called the lamina lucida
- the middle layer is called the lamina densa
- the bottom layer is called the lamina fibroreticularis
What is a glycocalyx?
a (microscopically) visible accumulation of sugars on the membrane proteins, lipids, polysaccharide chains etc.
Where is rRNA produced?
the nucleolus
What does the rough ER do?
synthesize proteins that are destined to become granules or be exported out of the cell
What is the function of the cell membrane?
act as a boundary to define compartments and regulate the flow of molecules in and out of compartments
how does a cell membrane appear on a TEM?
two electron dense lines bordering a less dense central zone
What is the function of the ribosome? What is it made of?
- to synthesize proteins (translate mRNA into an AA sequence)
- rRNA and protein
What occurs in the golgi apparatus?
- sugars are added to create glycoproteins
- granules form and may be released into the extracellular space
What do lysosomes do?
- contain hydrolytic enzymes to break down target molecules
- extracellular molecules can be targeted via endocytosis (pino or phagocytosis)
- intracellular molecules can be segregated via autophagy (contained within a vesicle) and then fused with the lysosome to degrade the molecules without degrading the cell
How do we differentiate between unfused and fused lysosomes?
- unfused lysosomes are called primary lysosomes
- fused lysosomes are called secondary lysosomes and may contain partially digested material
What does the smooth ER do?
- phospholipid and cholesterol synthesis
- detoxification of drugs (in the liver)
- the smooth ER is well developed in steroid secreting cells
What does the mitochondria do?
produce ATP via oxidative phosphorylation
Name the two molecules that are used to store excess glucose and excess lipids, respectively.
glycogen, triglycerides
Using a microscope, you see a cell containing a droplet of glycogen and a droplet of triglycerides. Are these droplets surrounded by a membrane?
No
What is a microtubule made of?
the protein tubulin, forming a hollow tube 25nm in diameter
In what locations can microtubules be found?
sperm tail, cilia, mitotic spindle, nerve cell axons, polarized cells, centriole
What are microfilaments made of?
polymers of the protein actin, 7nm in diameter
Name some functions of microfilaments
- generating movement (as in muscle cells)
- providing structure (as in the microvilli of the intestinal epithelial cells)
What is an intermediate filament made of?
there are many types that vary in composition, but are typically 10nm in diameter.
Name some functions of intermediate filaments
formation of a stable intracellular network, often linking to adjacent cells via intercellular junctions
Why are intermediate filaments important?
they can help identify cell types (only appearing in one or two cell types) and indicate disease states
What is an epithelial tissue?
a collection of adherent cells with little intercellular material, generally covering an external or internal surface of the body (epithelial cells in these conditions will have a free surface). The active cells (parenchyma) of endocrine/exocrine glands are also considered epithelial tissues
What are some functions of epithelial tissues? (6)
- protection and segregation of luminal space
- regulate surface transport
- absorption
- secretion
- sensation (rarely)
- production of eggs or sperm (rarely)
simple/stratified/pseudostratified epithelium
- simple - epithelium having only a single layer of cells
- stratified - epithelium having multiple layers
- pseudostratified - epithelium having a single layer, but not every cell reaches the free surface
squamous/cuboidal/columnar epithelium
- squamous - epithelial cells that are flat, with a nucleus that bulges out, width greater than height
- cuboidal - epithelial cells that are roughly spherical or cube shaped, width equal to height
- columnar - epithelial cells that are taller than they are wide
ciliated epithelium posses…
cilia
keratinized/nonkeratinized epithelium
- keratinized - superficial cells of this type of epithelium die and become tough and hard. No nucleus is visible in these deceased cells
- nonkeratinized - superficial cells are still alive
what is a serosal surface?
the surface of a body cavity, covered by epithelium. Serosal surfaces include the pericardial surface (heart) pleural surface (lungs) and peritoneal surface (abdominal)
Describe simple squamous epithelium. What are some examples and subtypes (2)?
simple squamous epithelium is a single layer of very thin cells with bulging nuclei. Simple squamous epithelium lines the blood cells (called ENDOTHELIUM) and the serosal surfaces (called MESOTHELIUM)
Describe simple cuboidal epithelium. What are some examples?
Cells may appear as cubes/squares or spheres/circles. Nuclei are located in the middle of the cells. Examples include certain kidney tubules and the parenchyma of the liver. These tissues are associated with secretion and absorption
Simple cuboidal epithelium is most often associated with…
secretion and absorption
Name some examples of simple columnar epithelium. What other cell type can also often be seen in simple columnar epithelium?
internal lining of intestines, immune cells
Describe pseudostratified columnar epithelium. Name some examples.
all cells are resting on the basement membrane but not all reach the free apical surface. Examples include the lining of the trachea, epididymis and the olfactory epithelium
Describe keratinizing stratified squamous epithelium. Name some examples.
keratinizing stratified squamous epithelium will have a layer of keratinized cells with no nuclei at the free surface. One example of keratinizing stratified squamous epithelium is the epidermis (skin)
Describe nonkeratinizing stratified squamous epithelium. Name some examples.
nonkeratinizing stratified squamous epithelium does not have a superficial layer of dead cells. Cells will have nuclei even on the free surface. This type of epithelium is found on moist surfaces such as the esophagus.
Name some examples of stratified cuboidal epithelium.
ducts of some glands, the cells of immature ovarian follicles
Name an example of stratified columnar epithelium
only found in certain glandular ducts
Why is transitional epithelium special? Where is it found? How can it be distinguished from other types of epithelium?
Transitional epithelial cells change shape. It lines urinary passages like the bladder which distend and relax. As the bladder distends, the number of cell layers appears to decrease. The most superficial cells are rounded, giving the edge a scalloped appearance.
The presence of keratins (cytokeratins) can indicate that a cell is or has originated from a(n)…
epithelial cell
Why do we describe epithelial cells as polarized?
there is an apical surface (near free surface) and basolateral surface (near membrane), that is, epithelial cells have an “up” and “down”. These surfaces have different functions and compositions
Name some apical specializations that epithelial cells can have as well as their primary components. (3)
- microvili - a fingerlike projection of the plasma membrane, held erect by actin microfilaments.
- cilia - larger than a microvilus, cilia are held upright via microtubules.
- stereocilia - very long microvili found ONLY in luminal epithelium of the epididymis and sensory cells of the ear. Composed of actin microfilaments
Name one function of microvili
increasing surface area for absorption
Name one function of cilia
cilia can beat to move fluid across the surface of the cell
All epithelial cells must have at least ONE surface….
contacting the basement membrane or basal lamina
What is a tight junction?
Tight junctions (zonula occludens) hold cells together “tightly”. The purpose of tight junctions is to keep liquid from escaping between cells, allowing a layer of cells (for instance, those lining an organ) to act as an impermeable barrier. For example, the tight junctions between the epithelial cells lining your bladder prevent urine from leaking out into the extracellular space.
What is a desmosome?
Desmosomes hold cells together via disc shaped plaques. They anchor sites for intermediate filaments, which invade the plaques. the cytoskeleton of all the cells in an epithelial sheet are connected, reinforcing it.
What is a hemidesmosome?
hemidesmosomes are found at the base of the cell and are linked to the BM (basement membrane). Intermediate filaments are anchored to the BM, increasing structural integrity. hemidesmosomes attach to a matrix, unlike desmosomes, which attach two cells together
What is a gap junction?
gap junctions transfer ions/small molecules between cells. communication between cells is the most common function
What is an exocrine gland?
a gland that secrete molecules through a duct to a site of action (sweat glands, mammary glands, etc)
- note the simplest exocrine glands may not have ducts, think the goblet cells that secrete mucus
- the epithelial cells often line the ducts
What is an endocrine gland?
glands that secrete molecules into the surrounding tissue or bloodstream (they never secrete direct to blood, the product must diffuse into the bloodstream from surrounding cells)
any molecule secreted by an endocrine gland is called a ….
hormone
complex secretory glands have one or more clusters of secretory cells called a _____ _______ that employ _____ ______ to carry secreted material to the site of action
secretory unit, excretory ducts
compound glands have…. ducts, compared to simple glands which have…. ducts
complex, branched duct systems, simple unbranched duct systems
acini (singular, acinus)
secretory units that are roughly spherical and have small lumens
alveoli (singular, alveolus, referring to a gland)
a secretory unit that has a large lumen
pancreatic secretory units are always called _____
acini
aside from acini and alveoli some glands may have….
tubular secretory units or lumens that are too small to see even with a light microscope
Myoepithelial cells
think myo=muscle. these cells surround secretory units and ducts and have some properties like epithelial cells and some like muscle cells. these cells contract to move secreted materials out of the gland along the ducts
Exocrine glands mostly fall into two categories based on their types of secretions
serous and mucous glands
Mucous glands primarily secrete…
mucus (a thick mixture of glycoproteins and polysaccharide rich molecules like proteoglycans)
- mucus is typically secreted in the digestive tract, respiratory tract etc.
- mucus secreting cells stain poorly with H&E
serous glands primarily secrete…
protein rich secretions that are watery and typically produced from eosinophilic like cells
exocrine glands that resist classification can be called
mixed sero-mucus gland
What is a mucous membrane? Name one special name we use for mucous membranes.
line spaces that open to the exterior of the body (GI tract, reproductive tract, etc)
- may contain glands (do NOT confuse it with the gland!!)
-when a mucous membrane has stratified squamous epithelium it is called a cutaneous mucous membrane
serous membranes
line serosal cavities
- the epithelium of a serous membrane is called MESOTHELIUM
What is mesothelium?
the epithelium that lines a serosal cavity as part of a serous membrane
True or false? Mucous membranes can never contain glands, but serous membranes do.
False, serous membranes do not contain glands while mucous membranes do
bright field microscopy
specimens are stained with dyes, then are visualized when light passes through them.
phase contrast microscopy/differential interference contrast microscopy
unstained specimens are viewed. living cells are often observed. objects are made visible due to the intrinsic optical properties of the object
how does electron microscopy work?
a beam of electrons interacts with the specimen
TEM
transmission electron microscopy - the beam passes through the specimen which is sliced very thinly and stained with heavy metals
SEM
scanning electron microscopy - the beam does not penetrate the specimen. and image of the surface is produced.
How are tissues prepared for light microscopy/tem?
- fixing - treating with a chemical to preserve the original structure of a tissue (crosslinking proteins with formaldehyde or glutaraldehyde), (denaturing proteins with acetic acid and ethanol)
- embedding - dried out tissue is imbedded in a firm medium (paraffin wax for light, plastic for TEM) so it can be sliced thinly without destroying it
- sectioning - slicing tissue into thin slices on a microtome and mounting it on a slide. The paraffin is dissolved away
- staining - TEM specimens are stained with heavy metals, light specimens are stained with hematoxylin and eosin (H&E)
eosin
acidic dye that binds to basic proteins, staining them pink or red
- stain intensity is correlated with protein content
- structures that stain heavily with eosin are called eosinophilic or acidophilic
hematoxylin
basic dye that stains acidic substances like nucleic acids.
- stains blue or purple
- materials that stain heavily with hematoxylin is basophilic
histochemical techniques
a way to detect biological molecules by performing chemical reactions directly on the session
- acid phosphatase can be detected by reacting it to form a brown product which can be visualized
fluorescence microscopy
tagging structures with fluorescent probes that glow under UV, then observing under microscope
immunocytochemistry
tagging structures with antibodies with fluorescent dyes attached, then observing
adipo- means
fat
chondro- means
cartilage
entero- means
intestine
gastro- means
stomach
histo- mean
tissue
kerato- means
‘horny tissue’
leuko- means
white
musculo- or myo- means
muscle
osteo- means
bone
pneumo- means
lung
reticul- means
branched net
trich- means
hair
-blast means
immature form
-clast means
destructive
-crine means
secretion
-cyte means
mature cell
-ferous means
carrying
-phil means
having an affinity for
-thelium means
cell layer
a- means
absence of
endo- means
within, inward
epi- means
on, upon
hypo- means
under
meso- means
middle, intermediate
meta- means
change, next
peri- means
around, near
cribosa means
having many perforations
fascicle means
bundle
lamina means
sheetlike layer or plate
lamella means
thin sheet or layer, diminutive of lamina
papilla means
cone shaped projection
parietal means
related to the wall of a cavity
septum means
wall or partition
sinus means
cavity
trabecula means
bundle of fibers or piece of spongy bone
tunica means
enclosing layer
What is a tissue?
A group of cells and their associated intercellular material that works together to perform specific functions
epithelial tissue…
largely cellular, with very little intercellular materials, covers or lines external or internal surfaces of the body
connective tissue…
fills the spaces between other tissues, providing support, strength, elasticity, or incompressibility depending on the nature of the matrix. in most cases there is a large amount of matrix
- this includes blood and lymph
Muscle tissue…
has well developed contractile properties, gives motility to organs and the organism, regulates blood flown
nervous tissue…
characterized by capacity to respond to a stimulus, to conduct an action potential and to initiate activity, permits interaction of the organism with the environment and integration of various bodily functions
physiology
the study of things moving, functions
anatomy/histology
form and structure
stress vs strain
stress is the force upon an object, strain is the deformation the object undergoes when subject to the force
flow
a form of strain that occurs when pressure is put on a liquid or gas, expressed as a rate (mL/hr)
osmotic/oncotic force
occurs when the solvent moves, not the solute (ie the movement of water)
Ohm’s law
V=IR, the amount of movement is proportional to the magnitude of the force and inversely proportional to the resistance (THIS WILL BE ON THE TEST)
- if you know two variables, you can estimate the third one
What are some general characteristics of epithelium (4)
- cells packed tightly together with little intercellular material/matrix
- cells have one free apical surface
- cells are supported by underlying connective tissue and are separated from it via basal or basement membrane
- epithelial sheet is avascular
ciliated pseudostratified epithelium is often found in…
the respiratory tract, epididymis, and olfactory epithelium
transitional epithelium is only found in…
the bladder
glandular epithelium
any epithelial cell or group of cell that is specialized for secretion
Holocrine secretions
occur when the cell is ripping itself apart to release the product, often losing cytoplasm
merocrine secretions
small vesicles fuse with the membrane to release product into the lumen
apocrine secretions
vesicles that fuse with the membrane to release product are larger than in merocrine secretions
True or false, the stomach is lined with goblet cells
False, the stomach is lined with mucus secreting cells but they are NOT goblet cells
secretory unit
the basic cluster of cells in the gland
mucus secretion
has lots of polysaccharides, but not a lot of protein, stain lightly
serous secretion
does not contain a lot of polysaccharides but is very protein rich, stain pink and are very eosinophillic
What is the stroma?
the supporting tissue or matrix of an organ
What is the parenchyma?
the essential or functional elements of an organ (secretory units, ducts)
Of all the different types of apical specializations, which is the largest? Which is the smallest?
stereocilia are much larger, microvili are much smaller than other apical specializations
Which component of the cytoskeleton do the actin containing microvilli and stereocillia attach to? It is best visualized in the brush border of the intestine
the terminal web
Which component of the cell do cilia attach to?
the basal body
What is the difference between motile and nonmotile cilia? How are their functions different?
motile cilia are used to push fluid in one direction. They occur in large amounts (an “army”
- they have a 9+2 arrangement of microtubules
- they are driven by dyein
nonmotile cilia are also called primary cilia.
- they have a 9+0 arrangement and have no dyein so they cannot move
- they have chemosensory function
Hemidesmosome
- allows the basal part of the cell to attach to the BM
- anchors the cell to the BM
Focal adhesions
a type of adhesion that anchors the cell to the BM
- stabilizes the epithelium
TIght junction (zonula occludens)
creates a dam or barrier between adjacent cells
- can prevent substances from leaking across the epithelium
- functions to compartmentalize the epithelium
gap junction
this type of connection utilizes connexon proteins to form a tunnel between two cells that molecules can diffuse through
- allows cells to communicate with eachother
cells or structures that stain strongly with hematoxylin are called
basophillic
cells or structures that stain strongly with eosin are called
eosinophillic
What is the term for the study of tissue?
histology
What does hematoxylin stain?
nucleic acids
What does eosin stain?
proteins, charged structures
True or false, epithelium is always highly vascular?
false, epithelium is avascular
This organ functions as both and endocrine and exocrine gland
pancreas
What are the 4 types of tissues
- connective
- epithelial
- nervous
- muscle
What are the two main types of epithelium?
glandular and nonglandular
Name some properties of connective tissue (6)
- bind tissues to form organs (support and binding)
- forms capsules around some organs
- anchors epithelium, provides blood supply
- is highly vascular (NOT CARTILAGE)
- has good repair potential
- cells can be similar or dissimilar
What is the most common type of connective tissue?
Fibrous
Fibrous connective tissue has three subtypes. What are they?
- dense
- loose
- reticular
Describe dense connective tissues and name an example
dense connective tissues are flexible, have high tensile strength, appear to have less cells and more extracellular fibers
- the dermis is a dense connective tissue
Describe loose connective tissues and name an example
loose connective tissues appear to be more cellular and have less extracellular fibers
- endometrial tissue is a loose connective tissue
Describe reticular connective tissues
reticular connective tissues appear like a ‘supporting mesh’
- this tissue is technically loose, but reticular fibers cannot be seen with H&E and must be silver stained
What is the extracellular matrix made of?
stroma and ground substance
What is the stroma composed of in fibrous connective tissue?
it is made of the proteins collagen and elastin
Describe the properties of collagen
it makes up 30-40% of your protein, has a high tensile strength and does not stretch
What are the two components of fibrous connective tissues?
- Extracellular matrix
- Heterogeneous cell populations
Describe the properties of elastin
it is stretchable protein, amounts of elastin in the stroma depends on the tissue (like arterial walls)
What is the ground substance?
ground substance is a gel in between cells and fibrous tissues, acting as a cushion and shock absorber
- it is composed of water and GAGs (glucosaminoglycans), hyaluronic acid, chondroitin sulfates, etc.
Describe resident cells of fibrous connective tissue and name some examples.
differentiate from mesenchymal (stem) cells, and have a life span of weeks to YEARS
- fibroblasts
- reticular cells
- adipose cells
- macrophages
- mast cells
Describe transient cells of fibrous connective tissue and name some examples.
these cells come and go through the tissues as needed
- neutrophils
- basophils
- monocytes
- eosinophils
What is a fibroblast?
a resident cell within connective tissues, it makes collagen, elastin, and GAGs.
- essentially it makes both the stroma and ground substance
What is a reticular cell?
a specialized fibroblast that secretes reticular fibers
- important in lymphoid organs/bone marrow
Describe adipocytes
adipocytes are fat cells that store energy, retain heat and absorb shock. they do not stain well with H&E. Common in the subcutis
What is a macrophage?
a “sentinel cell” that is a resident cell in connective tissue that works in inflammation and wound repair
What is a mast cell?
A “sentinel cell” that is a resident cell in connective tissue that works in inflammation and allergies
What are the two components of fibrous connective tissue?
ECM and heterogeneous cell populations
What is the most important resident cell of fibrous connective tissue?
fibroblast
What are three important characteristics of cartilage?
- it bears weight
- it spans spaces
- in young animals, it serves as a template for bone growth
True or false? Cartilage is an avascular tissue.
true
What two components make up cartilage?
cells and extracellular matrix
What are the three cell types that can be found in cartilage?
- chondroblasts
- chondrocytes
- chondroclasts
What do chondrocytes do?
These cells are not as active as chondroblasts. They secrete ECM and hang out in lacunae (‘lakes’)
What do chondroblasts do?
they secrete the chondroid matrix
What do chondroclasts do?
they resorb tissue and dissolve cartilage
What are the three types of cartilage?
- hyaline cartilage
- elastic cartilage
3.fibrocartilage
Name some characteristics of hyaline cartilage?
- cells embedded in matrix
- surrounded by a band of fibrous connective tissues (perichondrium)
Where can hyaline cartilage be found?
trachea, broncheal rings, larynx, nose end, articular surfaces, growth plates
What are some characteristics of fibrocartilage?
- appears to be organized into bundles
- chondrocytes are arranged in lines
- there are less chondrocytes and more collagen
Where can fibrocartilage be found?
intervertebral discs, menisci (of the knee), sympheses (pubic, mandibular), ligaments and tendons etc.
What are some characteristics of elastic cartilage?
- it is similar to hyaline cartilage, with more elastin fibers
Where can elastic cartilage be found?
in any pliable structure including
- the ear (pinna)
- the ear canal
- the epiglottis
(the three Es)
What are some characteristics of bone?
- highly dynamic and always changing
- made of connective tissues
- highly vascular
What are the functions of bone?
- internal support
- site of muscle attachment
- storage of calcium
What are the four types of cells found in bone?
- osteoprogenitor cells
- osteoblasts
- osteoclasts
- osteocytes
What do osteoprogenitor cells do? Where can they be found?
- they can be found in the periosteum and endosteum
- originate from mesenchymal cells
- differentiate into other cell types
What do osteocytes do? Where can they be located?
- live in lacunae of mature bones
- these cells are not mitotically active
What do osteoblasts do? Where can they be located?
- these cells form osteoid (unmineralized ECM)
- they can be found on surfaces of immature bone
What do osteoclasts do?
- these cells destroy bone for remodeling
What structure do osteoclasts make as they remodel bone?
Howship’s lacunae are formed when osteoclasts take a ‘bite’ out of bone
What are canaliculi?
channels in the bone that connect osteocytes/blasts and allow communication between cells
What is the mineral component of bone called?
hydroxyapatite
How much organic material is in a given bone? inorganic?
30% organic, 70% inorganic
The compressive strength of a bone comes from which component? is it stronger or weaker than the tensile strength?
compressive strength comes from the mineral component, it is much stronger than the tensile strength
Which component of bone does the tensile strength come from? Is it stronger or weaker than the compressive strength?
tensile strength comes from collagen. It is much weaker than the compressive strength
Of the four cell types in bone, which one is ‘the odd one out’ in terms of origin?
osteoclasts are the only ‘bone cells’ that originate from the macrophage cell line. The rest of the cells present in bone can be traced back to osteoprogenitor cells.
Name the two types of bone
- compact (cortical) bone
- spongy (cancellous) bone
What are the properties of compact bone? Where can it be found?
- provide strength to the exterior of the bone
- found on the outer wall of the diaphysis (shaft) of the bone
- made up of many dense lamellae (layers)
- osteocytes are found in lacunae, canaliculi contain cell processes
What is the name of the structures that contain blood vessels within compact bone
haversian canals
What is an osteon?
a haversian canal and concentric surrounding lamellae
What are the properties of spongy bone? Where can it be found?
- it can be found in the medullary cavity and epiphysis
- it is composed of trabeculae (thin bony projections)
- it does NOT contain haversian canals
- it is lined with endosteum
- it may have some lamellae
What is the periosteum?
a thin layer that surrounds the outside of a bone
What are the two layers of the endosteum?
- the dense connective tissue
- a thin layer of osteoprogenitor cells and osteoblasts
What is endosteum?
a thin layer of osteoblasts that lines the inner cavity, trabeculae, and haversian canals
What is muscle tissue?
tissue that is specialized to create movement by actively contracting
What are the three types of muscle tissue?
- skeletal
- cardiac
- smooth
What are the 3 connective tissue elements that form muscle fascia?
- epimysium - encapsulates entire muscle, continuous with the tendon
- perimysium - divides muscle into fascicles
- endomysium - surrounds each muscle fiber (cell), continuous with perimysium
Do skeletal muscle fibers have desmosomes and gap junctions?
No
Do skeletal muscles conduct action potentials?
yes
skeletal muscle cells are covered in this external glycoprotein layer into which fibers of the endomysium insert
external lamina
What name do we use for the place where a skeletal muscle cell is innervated via a motor neuron?
neuromuscular junction
The nerve terminal at the neuromuscular junction has synaptic vesicles that contain this neurotransmitter. The muscle cell has receptors for this neurotransmitter on its membrane.
acetylcholine
True or false? Skeletal muscle cells communicate with eachother
false, skeletal muscle cells are isolated from eachother and each responds independently from others
What is a T tubule?
tubular invaginations of the cell membrane that run into the cytoplasm, branching and surrounding the myofibrils
What is the function of the t tubules?
- to carry the action potential from the sarcolemma into the cell interior, associating closely with the sarcoplasmic reticulum (triggering Ca++ release)
- allows all sarcomeres to contract in sync
What do we call the units of contraction within the cytoplasm?
myofibrils
In skeletal muscle cells, myofibrils terminate on the….
plasma membrane
Are skeletal muscle cells uninucleated or multinucleated? Where in the cell is the nucleus located?
multinucleated, peripherally
Myofibrils are contractile units located within the muscle cells. What are myofibrils composed of?
sarcomeres
What are sarcomeres made of?
myofilaments (actin and myosin)
What are the two types of myofilaments?
thin and thick filaments (actin and myosin)
Where are thick filaments anchored?
at the Z disc
What are thin filaments composed of?
actin
What are thick filaments composed of?
myosin
What is the Z disc?
a flat disc of proteins onto which the thin filaments insert
Describe the different regions of the sarcomere?
- A band - the main dark band in the middle of the sarcomere (has both types of filaments)
- H band - the slightly lighter central line in the A band (has no thin filaments)
- I band - lighter band that has only thin filaments
- Z line - the line in the middle of the I band, caused by the Z disc, where thin filaments insert
- M line - a central dark line in the A band, where thick filaments insert
What is the sarcoplasmic reticulum?
an organelle derived from the smooth endoplasmic reticulum. It forms a network between and around the myofibrils.
Describe how cardiac muscle looks.
the cells are connected via intercellular junctions and are branched (UNLIKE skeletal muscle), are striated and have myofibrils and sarcomeres (LIKE skeletal muscle)
What is the name of intercellular junctions between cardiac muscle cells?
intercalated discs
intercalated discs are typically home to this structure related to intercellular communication
gap junction
Cardiac muscle cells also utilize this structure to link cells together
desmosomes
How many nuclei do each cardiac muscle cell have?
just one or two centrally located nuclei
True or false? Smooth muscles are anchored to bone
false
Describe the cell shape of smooth muscle cells.
fusiform (spindle shaped)
True or false? smooth muscle cells have sarcomeres and thus appear striated.
false, actin and myosin are not organized into sarcomeres and thus are not striated
What is the special term we use for invaginations of the sarcolemma of smooth muscle?
caveolae
True or false? Smooth muscles do not have gap junctions like skeletal muscle
False, smooth muscles use gap junctions
How many nuclei do smooth muscle cells have?
one
Give an example of skeletal muscle
muscles that are under voluntary control, such as those that move the skeleton, eyes and tongue
Name the three connective tissue layers that bind the parts of the muscle together.
- epimysium - covers the whole muscle
- perimysium - creates bundles of cells
- endomysium - surrounds individual cells
What are the functions of muscle fascia?
- group muscle cells together
- bring cells together into a functional mass
- resist overstretching
How is skeletal muscle innervated?
each individual muscle cell is isolated, and must be innervated by its own terminal branch of a motor neuron
Describe the action potential and contraction of a muscle cell (5)
- release of acetylcholine (ach) into synaptic cleft, which goes on to bind to ach receptors
- sodium channels open and the membrane depolarizes
- membrane action potential is transmitted into the cell by the T tubules
- Ca++ is released into the sarcoplasm from sarcoplasmic reticulum
- myofilament sliding and muscle contraction
What is the function of intercalated discs?
- mechanical attachments (transmission of forces of contraction via fascia adherens and desmosomes)
- Electrical conduction - allows spread of membrane action potential (gap junction)
What is a purkinje fiber?
they carry electrical impulses to the heart
How is smooth muscle controlled
- the autonomic nervous system, hormones, and local metabolites modulate the contractions of smooth muscle
- this muscle is not under voluntary control
What is the functional unit of smooth muscle called?
Fasciculi - irregularly branching bundles of fibers that are often loosely arranged in sheets
Smooth muscle does not have T tubules. What structure does it have instead?
caveolae
In smooth muscle, what do dense bodies do?
anchor points for thin filaments (actin), occuring on the plasma membrane and in the cytoplasm
- they act similarly to the Z disc (an actin anchor point)
In smooth muscle, what is the external lamina?
an external glycoprotein coat that may merge between cells and form linkages
