Tissues Pt.2 Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Bone

A

bone is connective tissue

Hard, calcified CT

2 meanings:

Osseous tissue

(2 types = spongy bone & compact)

OR

Organ, named bone = more than just osseous tissue)

General features of bone as an organ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

typical long bone

A

Typical Long Bone

2 types = spongy

(trabecular / cancellous - strength with reduction in weight) + compact

Organ = other tissue

types: epithelium,
nervous and other types of CT

Functions: support, protection; attachment site for muscles (levers);
marrow = blood formation; electrolyte balance; pH balance;
detoxification (repository)

Diaphysis - growing through

Epiphysis - growing upon

Epi = in addition, upon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

bone cell (4)

A

Deposition = osteoblasts

(lay down bone tissue - non-mitotic)

Maintenance = osteocytes

Remodelling = osteoclasts

(multinucleate cells, bone macrophages)

Macrophage = large eater

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q
A

Bone = cells + matrix

Organic (1/3) = collagen fibres +
protein & carbohydrate complexes

Collagen = resistance to twisting and
bending forces (bone is brittle in its absence - shatter)

(Osteogenesis imperfecta = brittle bone disease)

Inorganic (2/3) = calcium salts (mainly
calcium phosphate salts)

Bone loses rigidity in its absence
(Rickets & Osteomalacia - soft bones)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

epiphyseal line

A

mature, represents bony joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

osteocytes and canaliculi

A

Osteocytes nourished via diffusion

  • facilitated by gap junctions between cells.

Cell processes travel through small canals called canalicili.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

epiphyseal plate

A

epiphyseal plate = growing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

compact bone

A

Units of bone structure = osteon

= concentric rings of bone

Outer bone

  • circumferential lamellae

Blood vessels
- central artery & vein.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

muscle, stuff to know!!

A

must be able to describe the characteristics, function and location of different types of muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

overview of muscle

A

3 types: skeletal, cardiac and smooth.

All forms are:

  • Excitable
  • Extensible - able to stretch between contractions
  • Elastic - recoil
  • Contractile
  • Highly cellular
  • Well vascularised
  • All contain large numbers of the myofilaments required for contraction.

The 3 types of muscle differ in terms of:

  • Where they are found
  • Structure of their cells
  • How they are activated to contract

Main functions relate to:
* Movement
* Stabilisation (e.g. around joints)
* Maintenance of posture
* Generating heat (skeletal muscle - shivering during cold stress)
* Blood glucose regulation (absorb, store & use glucose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

skeletal muscle (voluntary and striated)

A

Striated = cross-striations across the muscles cells.

Control is largely voluntary but reflex (involuntary) movements are also possible.

Most is attached to bone - movement
of appendicular and axial skeleton.

BUT

Visceral striated muscle = morphologically identical to skeletal
muscle but restricted to soft tissues.

Examples: tongue, pharynx, upper part of the esophagus, lumbar part of the diagram (speech, swallowing &
breathing).

Contraction = rapid BUT skeletal muscle tires quickly and
requires rest to recover.

Refractory period = 1-2 milliseconds.
(RP = time between when muscle is stimulated to contract and how long before it can be stimulated again).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q
A

A named muscle is a discrete organ - contains many muscle fibres (cells), lots of connective tissue, which carries blood vessels and nerves.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q
A

Terminology:

Myo = muscle

Myofibre* = muscle cell

Sarco = flesh

Sarcolemma = cell membrane (lemma = husk)

Sarcoplasm = cytoplasm

Sarcoplasmic reticulum = SER (reticulum = little net) - calcium storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

muscle fibre

A

Long protein cords = myofibrils

  • Lots of mitochondria - packed into spaces between myofibrils
  • Abundance of glycogen stored as granules called glycosomes (= glycogen bodies)
  • Each myofibril = a bundle of parallel
    protein microfilaments = myofilaments

3 types of myofilaments:
* Thick filaments = myosin
* Thin filaments = actin AND
* Elastic filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q
A

Individual skeletal muscle cells are cylindrical.

Typical muscle cell is about 100 umetres in diameter (may be as great as 500 metres) and from 3 - 30cms long (but can be up to 1m).

Due to their length skeletal muscle cells are termed myofibres (muscle fibres).

Multinucleated cells = fusion of cells called myoblasts during
embryonic development.

Each myoblast contributes its nucleus.

Syncitium: syn = together; -cytium = cells.

Functionally acting together as one cell.

Nuclei are positioned against the cell membrane = peripherally placed.

Some myoblasts remain as unspecialised satellite cells - role in regeneration of damaged skeletal muscle.

BUT

Limited possibility for repair - in adults, skeletal muscle cells are not able to replicate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

need to know about striations

A
  • An individual muscle cell contains lots of myofibrils.
  • Each myofibril is made up of hundreds of sarcomeres arranged end to end.
  • Sarcomeres = contractile units of the muscle fibre.
  • Muscle contraction occurs because actin and myosin filaments slide over each other = shortening of the sarcomere = sliding filament theory.
  • Shortening of hundreds of end
    to end sarcomere = shortening
    of entire muscle.
10
Q

Motor Neurons & Motor Units

A
  • Skeletal muscles are innervated by nerve fibres that arise from the brain stem and the spinal cord.
  • If the nerve fibres are damaged, skeletal muscle cannot contract.
  • Each nerve fibre branches out to supply multiple muscle fibres.
  • Each individual muscle fibre (cell) receives its nerve supply from the terminal branching of a nerve.

(Electrically insulated due to amount of surrounding connective tissue)

  • All muscle fibres innervated by the terminal branchings of a single nerve behave as a functional unit.
  • One nerve fibre + all the muscle fibres it
    innervates = motor unit.
10
Q

Motor units

A

~200 muscle fibres are innervated by each motor neuron

BUT the structure of motor units relates to their function.

Fine control = 1 motor neuron + 3-6
muscle fibres (cells) = small motor units.

Examples = muscles of eye movement & hand.

Strength = 1 motor neuron + up to 1000 muscle fibres (cells) = large motor units.

Examples = postural and locomotor
muscles (back & lower limbs).

Multiple motor units in each muscle = some able to rest & recover while some are active
= differential rates of fatigue in a muscle units allow for sustained muscle function.

11
Q

cardiac muscle (involuntary and striated)

A

Cardiac muscle = heart only

Starts beating by week 4 of embryological development and never stops until you die

Cells are called cardiomyocytes (cardiocytes).

Cardiocytes:

  • are shorter than skeletal muscle (50-100 umetres and thicker relative to their their size (10-20 umetres).
  • can contract without nervous stimulation = autorhythmic BUT moderated by autonomic nervous control (sympathetic & parasympathetic)
  • contain a single nucleus
  • are branched cells
  • are rich in glycogen (energy store)
  • exhibit specialised junctions with each other = intercalated discs
  • exhibit a low level of cell division (1%) but insufficient to repair damage. No satellite
    cells. Damage = scarring.
12
Q

Intercalated discs (2 parts):

A

Intercalated discs (2 parts):

  • Mechanical junctions = desmosomes = tissue integrity: keeps cells firmly bound to each other.
  • Electrical junctions = gap junctions; allows each cardiocyte to directly stimulate adjoining cells.
  • Cardiac muscle acts as a syncytium (= all cells acting as one)
  • Electrical barrier between atria (thin walled chambers) and ventricles (thicker walled) of the heart.
  • Atria contact together; ventricles contract together.
  • Cardiac muscle refractory period = 250 milliseconds - allow?) for full ejection of blood from chambers before refilling.
12
Q
A

TEM - note the following:

Presence of sarcomere (same contractile units as skeletal muscle); abundant mitochondria; intercalated discs (electron dense) = desmosomes + gap junctions

13
Q

smooth muscle (involuntary and non-striated)

A

= visceral muscle (viscera = internal organs)

Found in the walls of organs, usually layered - depends on location

Like cardiac muscle is auto-rhythmic so can contract independent of nervous stimuli

Responds to multiple stimuli - chemicals, hormones, pH, CO2, 02, temperature, stretch.

Specialised for slow, prolonged contraction

13
Q

mitochondria in cardiac muscle

A
  • Mitochondria in cardiac muscle are larger and more abundant compared to skeletal muscle.
  • Mitochondria occupy ~ 25% of the cell in cardiac muscle

(skeletal muscle mitochondria ~ 2%)

14
Q

smooth muscle cells

A

Smooth muscle cells:

  • can secrete connective tissue matrix (well developed RER and Golgi) - collagen, reticular fibres & elastin (depends on location).
  • are capable of cell division to maintain or increase their numbers.

Gap junctions are produced according to need (e.g. uterus during pregnancy)

14
Q
A

Cells are fusiform in shape (wide middle with tapered ends). Range in length: 20 umetres = small blood vessels;

200 umetres = intestinal wall; 500 umetres = wall of uterus during pregnancy

Non-striated appearance because contractile elements are not arranged in regular repeating units as is the case for skeletal and cardiac muscles

Dense bodies are analogous to the Z lines in striated muscle (Z lines demarcate sarcomeres).
They anchor the thin (actin filaments).

Nuclei can have a corkscrew appearance in contracted SM

14
Q

how do smooth muscle cells communicate

A

they communicate via gap junctions (can act like a syncytium)

14
Q

comparing muscle types in histological sections

A

Histological characteristics of the 3 muscle types differ according to:

  • Presence or absence of striations
  • Cell shape (cylindrical, branching, fusiform)
  • Cell length (long vs short)
  • Number of nuclei in a cell (one vs several)
  • Position of nuclei (peripheral vs central)
  • Intercalated discs (present vs absent)
15
Q

muscle in cross section

A

Increase in the size of skeletal and cardiac muscle occurs via hypertrophy

(hyper = over; trophy = nourishment)
Increases in smooth muscle occurs via hypertrophy and hyperplasia
(-plasia = formation)

16
Q
A

Objective: Describe the characteristics, function and location of the different types of muscle.

Example Exam Question: Compare and contrast the structural features of cardiac and smooth muscle.

Compare = what do they have in common?

Single, centrally placed nucleus;
Same contractile elements (actin and myosin);

Both have gap junctions;

Both are short relative to skeletal muscle

Contrast = how do they differ?
Intercalated discs in CM; dense bodies in SM

Different cell shape (cardiac = branched; smooth = fusiform);
CM is striated; SM is not;

Not relevant to this question = involuntary; each behaves as a syncytium.

17
Q

shape of smooth muscles

A

Cells are fusiform in shape (wide middle with tapered ends). Range in length: 20 metres = small blood vessels;

200 metres = intestinal wall; 500 metres = wall of uterus during pregnancy

Non-striated appearance because contractile elements are not arranged in regular repeating units as is the case for skeletal and cardiac muscles

Dense bodies are analogous to the Z lines in striated muscle (< lines demarcate sarcomeres).

They anchor the thin (actin) filaments.

They also anchor smooth muscle cells to each other.

17
Q

smooth muscle

A

= visceral muscle (viscera = internal organs)

Found in the walls of organs, usually layered - depends on location

Like cardiac muscle is auto-rhythmic so can contract independent of nervous stimuli

Responds to multiple stimuli - chemicals, hormones, pH, COz, 02, temperature, stretch.

Specialised for slow, prolonged contraction

18
Q

Histological characteristics of the 3 muscle types differ according to:

A
  • Presence or absence of striations
  • Cell shape (cylindrical, branching, fusiform)
  • Cell length (long vs short)
  • Number of nuclei in a cell (one vs several)
  • Position of nuclei (peripheral vs central)
  • Intercalated discs (present vs absent)
18
Q

smooth muscle cell communication

A

smooth muscle cells communicatre via a gap junction (can act like a syncytium)

18
Q

muscle in cross-section

A

Increase in the size of skeletal and cardiac muscle occurs via hypertrophy

(hyper = over; trophy = nourishment)

Increases in smooth muscle occurs via hypertrophy and hyperplasia
(-plasia = formation)

cardiac is single nucleus, centrally placed, striated, involuntary with intercalated disks, branched shape.

smooth is single nucleus, centrally placed, non-striated, involuntary without intercalated disks, fusiform shape.