Quiz 2: Muscular, Cardiac, and Respiratory Development and Feeding

What are the characteristics of muscles?

excitability, contractility, extensibility, elasticity

Smooth (involuntary) muscle

What muscle tissue is this?

What are the characteristics of smooth muscle?

smooth, non-striated, spindle-shaped cells, and a central nucleus

Where is smooth muscle located?

walls of the digestive and urinary systems, and blood vessels

What is the purpose of smooth muscle?

decrease the structure size and peristalsis

Cardiac muscle

What muscle tissue is this?

What are the characteristics of cardiac muscle?

striated, irregularly shaped, with one central nucleus

Skeletal (Voluntary) muscle

What muscle tissue is this?

What are the characteristics of skeletal muscle?

striated, multinucleated, energy-consuming tissue

What is the function of skeletal muscle?

movement, postural stability, joint stability, head production

Is more energy spent to produce movement or heat?

heat

What are the organizing structures of skeletal muscle?

epimysium, perimysium, endomysium, fasciculi, myofibers, myofibrils, myofilaments

What is the epimysium?

dense CT that surrounds the entire muscle tissue

What is the perimysium?

CT that surrounds each bundle of muscle fibers (fasciculi)

What is the endomysium?

CT that covers each single muscle fiber/cell (myofiber)

What are the fasciculi?

bundles of individual muscle cells (myofiber)

What CT surrounds the individual fasciculi?

perimysium

What are the myofibers?

fibers that combine to make the fasciculi

What CT surrounds the individual myofibers?

endomysium

What are the myofibrils?

actin and myosin as an active contractile component

What are the myofilaments?

actin and myosin proteins (individually)

What is the function of somites?

form bone, CT, and skeltal muscle

When do somites arise?

during neurolation

What is the function of myogenic precursor cells (MPCs)?

undifferentiated cells that become active after injury to differentiate into muscle cells (myocytes)

What is the function of myoblasts?

produce actin, myosin, and myotubes

What are myotubes?

immature, multinucleated muscle cells

What do the myotubes contain?

contractile proteins (actin and myosin)

What is the general function of myotubes?

to fuse together to form myofibers

When do primary myotubes develop?

~8 weeks GA

What do primary myotubes become?

type 1 (slow-twitch/endurance) muscle fibers

What do secondary myotubes require before they can develop?

Innervation

When do secondary myotubes develop?

Few weeks after primary

What do secondary myotubes become?

type II (fast-twitch/speed) fibers

By 21 weeks (PMA), what fibers have a higher ratio in the developing fetus?

type II

What are the consequences of the imbalance of Type II > Type I fibers in preterm infants?

Faster fatigue than term-born infants, especially in the respiratory muscles

When do type I and II fibers become =?

by 40 weeks (PMA)

What are myofibers?

mature, multinucleated muscle cells

What are the characteristics of myofibers?

Have the striated appearance of muscle cells

What are fibroblasts?

precursor cells to the perimysium and epimysium

What is the function of satellite cells?

necessary for muscle growth during infancy and repair later in life

What does the neuromuscular junction (NMJ) look like ~ 8 weeks GA?

Each motor endplate has multiple innervations

What does the neuromuscular junction (NMJ) look like at 20-32 weeks GA?

Innervations will decrease to allow for mono-innervated motor end plates

What occurs between 20-32 weeks and decreases the number of innervations at each NMJ?

massive nerve cell apoptosis

By when are nearly all skeletal muscles present during embryonic development?

end of embryonic period (~10 weeks GA)

What are the 6 different processes of muscle development?

reorientation, remain parallel, split longitudinally or layers, degenerate, or migrate

What happens when muscle fibers reorient during development?

may change from original cephalo-caudal orientation

What happens when myotomes that do not redirect from the cephalo-caudal orientation fuse?

from composite muscles

What are composite muscles?

muscles that remain parallel to the long axis of the body (e.g. erector spinae and rectus abdominis)

What occurs when myotomes split longitudinally?

form 2 or more parts that become separate muscle heads (e.g. biceps brachii)

What happens when myotomes split into layers?

Form layered muscles (e.g. intercostals)

What happens when muscles degenerate during development

they form aponeurosis (e.g. plantar apo.)

What happens when muscles migrate during development?

move to more remote regions (e.g. lats)

When does a small amount of hyperplasia occur after birth?

1st year

How do satellite cells respond to postnatal active strengthening?

generate new myofibrils

How do satellite cells contribute to postnatal muscle length?

lengthen serial sarcomeres in response to passive stretch

What are the other postnatal roles of staellite cells?

supply nuceli to enlarging fibers and repair muscle after injury

What does muscle fiber diameter growth depend on during development?

PA; inc. PA intensity leads to new myofibrils

What does muscle fiber length growth depend on during development?

skeletan growth; passive stretch causes serial growth (lengthening) of muscle

When does postnatal fiber differentitation occur?

into young adulthood due to demand response

What does the difference in gene expression for children with CP cause?

increase in ECM causing less contractile tissue

How does increasing ECM affect kids with CP?

inc. [collagen], atypical organization, 40% muscle tissue (95% in kids w/out CP), 1/2 the satellite cells

How does having 1/2 the satellite cells affect kids with CP?

dec. overall sarcomere length

How does decreased sarcomere length affect kids with CP?

dec. ROM during growth and elongation of sacomeres w/poor actin-myosin contact

Does type I and type II differentiation continue into adolescence?

yes

What are the hormones that contribute to strength development?

Testosterone, estrogen, insulin, GH, TH

What do the ventricles arise from?

embryological heart begins as a tube that gives rise to these

What do the atria arise from?

sacculations that form above the ventricles

What is the function of the foramen ovale?

allow blood to shunt from left to right atria in untero

What is the 1st step in fetal circulation?

O2 blood from IVC (placental circ.) enters R.A. and moves through the F.O. into the L.A.

What is the 2nd step in fetal circulation?

O2 and no O2 blood in the L.A. mix and enter the fetal circulation

What is the 3rd step in fetal circulation?

[O2 blood] flows into the carotid arches to supply the brain

What is the structure called that allows the O2 and non-O2 blood to mix?

ductus arteriosus

What is the 4th step in fetal circulation?

remaining partially O2 blood mixes w/ non-O2 blood and circulates into the fetal body

How does the foramen ovale and ductus arteriosus close?

at birth with the first inflation of lungs (inc. P)

When does mature circulation begin?

minutes to hours after birth

What is the newborn lung like?

Diaphragm has too few type I muscle fibers and alveoli not fully formed

When do the ribs begin to angle downward?

after infant can sit upright (~6 months)

What is secondary respiration muscles and when does it begin?

SCM, intercostals, and abdominals; ~6 months

When do preterm infants begin bottle feeding?

by 35 weeks if healthy

When should you be concerned about pre-term babies bottel feeding duration?

if it consistently lasts > 30 minutes

What are the signs of readiness to begin oral feeing with preterm babies?

rooting reflex, flexion in arms/legs, awake status, sucking (paci or hands), non-nutrient suckling (~ 28 wks)

What is the rooting reflex?

Brushing an infant's cheek will cause the baby to turn in that direction.

What does proper positioning for a bottle or breastfeeding look like?

close, eye contact, head in midline w/ support, swaddling, hips blw head

What are the signs of readiness for solid foods?

indp. head holding, prop-sitting, 2x Bw, open mouth when presented with a spoon

When does rotary chewing begin? What does this mean?

12-17 months; can introduce spoons and crackers

Why should babies under 12 mnth not have juice?

Unneedeed calories and harmful to teeth