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Physiology > Week 10 > Flashcards

Week 10 Flashcards

1
Q

What are the key functions of the skeletal system?

A
  1. protects internal organs: Brian and lungs
  2. facilitates movement: skeletal muscle, tendon, ligament, cartilage
  3. supports body
  4. stores and releases fat: bone marrow
  5. stores and releases minerals: Ca2+, PO4,3-
  6. produces blood cells
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2
Q

What is the axial skeleton comprised of?

A
  • skull
  • vertebrae of spine
  • thoracic cage (ribs and sternum)
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3
Q

what is the appendicular skeleton comprised of?

A
  • upper and lower limbs
  • pelvis
  • pectoral girdle (shoulder)
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4
Q

What are the key components of the connective tissue?

A
  1. cells - small volume
  2. extracellular matrix
    - fibres eg. collagen, elastin
    - ground substance (gel between fibres)
  3. organic matrix in bone
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5
Q

What is the ground substance comprised of?

A

portroglycan - fills space between fibres, provides swelling pressure
glycosaminoglycan
water and electrolytes, contributes to swelling pressure

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6
Q

What are the two types of connective tissue?

A

loose, dense (skeletal tissues are dense connective tissues)

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7
Q

What fires are there in connective tissue?

A
  1. collagen (29 diff types), most abundant protein in body, provides tensile strength, helical
  2. Elastin, allows to recoil after stretch, mesh
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8
Q

What is the structure of the bone?

A
  • cortical bone (very dense): outer layer- periosteum, inner layer- endosperm
  • spongy bone (less dense)
  • bone marrow
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9
Q

What are the two types of bone marrow?

A

red - site of production of blood cells
yellow - fat storage site
- proportion changes w age, red decreases

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10
Q

Explain the different type of bone cells

A

outside: osteogenic cells (stem cell)
route 1: differentiate into osteoblast - line surface of bone, creates ECM, lays down minerals, surround themselves with bone besides leaving small channels
route 2: differentiate into osteocytes - sense nature of bone in terms of how they respond to leading, signal other cell types to make/ break

osteoclasts - distinct form the rest, further in

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11
Q

What is the origin of osteoblasts and chondrocytes?

A

mesenchymal stem cells

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12
Q

what is the origin of osteoclasts?

A

hematopoietic stem cells

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13
Q

What are the two types of bone formation?

A

interamembranous
endochondral

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14
Q

How does intra-membranous ossification work?

A
  • directly from undifferentiated mesenchymal connective tissue
  • occurs only in some bones: skull, flat bones of face, clavicle (collarbone)
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15
Q

How does endochondral ossification work?

A
  • via cartilage intermediary
  • occurs only in most bones (except skull, collarbones)
  • growth plate
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16
Q

What are the zones of the growth plate?

A

outside to inside
- reserve zone
- proliferative zone
- hypertrophic zone (cells get larger)
- calcification (mineralised cartilage, cell death)
- ossification (mineralised cartilage remodelled to form bone)

17
Q

What does the growth plate allow for?

A

growth of bone length

18
Q

How does bone formation occur for fracture healing?

A
  • directly building new bone onto fracture site (direct or contact healing)
  • heal in a process similar to endochondral ossification - via cartilage intermediate (intermediate healing)
19
Q

control of bone maintenance

A

bone formation (osteoblast activity - reduces blood Ca2+)
bone resorption (osteoclast activity - increased blood Ca2+)
also impacts on growth plate - bone elongation

20
Q

Why is it so important to maintain blood Ca?

A

too little
- muscle twitching/ spasm
- numbness
- paresthesia

too much
- thirst/ frequent urination
- digestive distress
- bone pain
- muscle weakness
- fatigue
- cardiac arhythmia
- kindey stones

-> needs a higher conc inside to trigger depolarisation, if conc is too similar its harder, if conc is too steep, too easy -> spasm

21
Q

What hormones are involved in control of bone maintenance?

A
  • GH - anterior pituitary - increases length, improves density
  • Thyroxine -thyroid - stimulates bone growth, promotes synthesis if bone matrix
  • calcitriol (vitD) - stimulates osteoclast proliferation, resorption of bone by osteoclasts
  • calcitonin - thyroid - inhibits osteoclast activity and stimulates calcium uptake by bones
22
Q

What does Wolff’s law state?

A

form follows function

23
Q

What does mechanical strain lead to?

A
  • re-distribution of Ca2+ between the blood and bone tissue
24
Q

How does mechanotransduction in the bone work?

A
  • mesenchymal stem cells
    -> osteoblasts
    -> osteocytes
    -> intern, primary cilium, piezo1 channel
25
Q

Explain the effect of growth hormone on bone maintenance

A
  • somatotropin
  • produced by pituitary, increases muscle mass, fat, radial bone growth
  • liver produces insulin like growth factor 1(IGF-1) -> -ve feedback, decrease of GH
26
Q

What is the difference in effect of GH in youth and adults?

A

youth: growth plate sill open, adds to length and thickness
adulthood: growth plate closed, adds to thickness

27
Q

Explain the effect of thyroxine on bone maintenance

A
  • no targeted effect on bone tissue, but general metabolic effects on all tissue
  • promotes release of GH through positive feedback of pituitary
28
Q

Explain the effect of sex hormones on bone maintenance

A
  • promotes bone formation/ maintenance of bone density
  • promotes closure of growth plate
  • oestrogen in females
    early growth plate closure - reduced bone length
    reduction at menopause leads to loss of bone density
29
Q

What are the combined actions of androgens and estrogen?

A
  1. increased trabecular mineral and thickness
  2. increased cortical thickness
  3. increased periosteral expansion
30
Q

Explain the effect of vitamin D on body maintenance

A
  • vit D3 = steroid hormone
  • 7-dehydrocholesterol (via skin) -> ergocalcipherol (pre-D3) -> cholecalciferol + food intake -> via liver, kidney and parathyroid hormone -> calcitriol active vitamin D3
31
Q

functions of vitamin D

A
  • facilitates intestinal absorption of calcium (also phosphate and Mg2+)
  • vit D binds to intracellular receptor - VDR + Vit D binding site, VDR also has DNA binding site
  • complex of VD3-VDR bound to DNA stimulates expression of a number of proteins
    -> calc transporters (calbindin)
    -> bone matrix proteins (osteocaclin)
    -> suppresses synthesis of type 1 collagen
32
Q

What homines are in the thyroid/ parathyroid produced?

A
  • calcitonin
  • parathyroid hormone
33
Q

What is the function of bone tissue?

A

Ca2+ reservoir

34
Q

Describe the pathway for too little Ca2+

A
  • more PTH
  • more osteoclasts
  • more ca 2+ uptake from blood stream
  • more cholecalcipherol
  • more cacitriol in liver
  • more intestinal uptake
35
Q

Describe the pathway for too much Ca2+

A
  • positive feedback for CT
  • positive feedback for osteoblasts
  • negative feedback for osteoclasts
  • osteoblasts increase uptake of Ca2+ from bone tissues
36
Q

name two different bone- related disorders

A
  1. osteoporosis
    - porous bones
    - aging- related
    - increased osteoclast activity
  2. osteochondrosis
    - abnormal growth plate
    - typically in childhood and adolescence

Physiology (18 decks)

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