Week 1 MSK

ECM

contains fluid transporting nutrients to cells, carrying away their wastes and secretory products

Epithelial tissue function

lining of body cavities, glandular secretion

CT function

structural support, nutrition, storage (fat, water, electrolytes), defense, repair, information

Most abundant CT cells?

Fibroblasts

Fibroblast function

synthesize and secrete fibers and ground substance, create and export factors to influence adjacent cell growth and proliferation

Adipocyte function

store fat, produce hormones and cytokines responsible for metabolism and immune health

What are macrophages derived from?

Monocytes

Macrophage function

phagocytize foreign particles, microorganisms, and damaged tissues, initiate immune response, initiate turnover of ECM

How do macrophages initiate immune response?

Present antigens to lymphocytes, secrete cytokines

What are cytokines?

Cell-signaling proteins

How do macrophages initiate ECM turnover?

Secrete hydrolytic enzymes (collagenase)

What are the four main cells in CT?

fibroblasts, adipocytes, macrophages, mast cells

What are mast cells

WBC commonly in CT

Mast cell functions

Chemical mediators of inflammatory response, allergic reactions

Chemical mediators of mast cells

histamine, heparin, eosinophil chemotactic factor, etc.

Collagen type I

thick collagen found in CT (tendons, skin, organs)

Collagen type III

reticular fibers, flexible meshwork (smooth muscle, endocrine glands, liver)

What do elastin fibers contain?

elastin and fibrilin

Elastin fiber locations

skin, trachea

Transient cells of CT

plasma, leukocytes (eosinophils, lymphocytes, neutrophils)

What is the most widespread CT?

Loose CT

Loose CT properties

ground substance/cells > fibers, contain collagen, reticular, and elastic fibers, loose irregular meshwork, flexible, vascularized, slight resistance to stress

Loose CT locations

Stomach/intestinal epithelia

Loose CT functions

cushions organs, storehouse of immune cells for many organs, can reduce inflammation

Dense Irregular CT properties

collagen fibers in 3D network, consist of mostly fibroblasts, resist pressure in many directions

Dense Irregular CT locations

dermis, gut, surrounding organs

Dense Irregular CT functions

give structural strength/flexibility to organs

Dense Regular CT properties

collagen fibers lay parallel to each other, primarily fibroblasts, resistant to pressure along one plane

Dense Regular CT locations

tendons, ligaments

What are the two types of adipose tissue?

unilocular (white), multilocular (brown)

White fat function

fat storage

Brown fat function

generates heat in newborns/fetuses

Elastin properties

dense, irregular elastic tissue

Elastin locations

Middle layer of large arteries, some ligaments

Reticular locations

hematopoietic bone marrow, lymph nodes, spleen

What is the major determinant of the properties of cartilage?

ECM composition

How is cartilage different from every other form of CT?

It is avascular and only has one type of cell (chondrocytes)

What is the most common form of cartilage?

Hyaline cartilage

Hyaline cartilage locations

Large airway walls, ends of bones in synovial joints, epiphyseal plates in youth

Hyaline cartilage function

Provide smooth gliding surfaces for bones, support body structures

Elastic cartilage function

facilitates speech, provides flexible support to larynx

Fibrocartilage locations

vertebrae, pubic symphysis, some tendon/ligament attachments

Fibrocartilage function

shock absorption, prevent bone to bone contact

Bone function

Provide structure of body, protect internal organs, act as lever for muscles to act on, house and protect CNS, form RBCs, reservoir of Ca2+

What are the four types of bone cells?

Osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts

Osteoprogenitor cell function

stem cells to become osteoblasts

Osteoblast function

development of bone matrix (osteoid) and initial mineralization, which form osteocytes

How long can osteocyte cells live?

20-30 years

Osteoclast function

Removal and turnover of bone matrix by secreting bone degrading enzymes and hydrogen ions

Periosteum properties

Cover outer surface of bones, contain BVs and nerves, fibroblasts generate collagen fibers to link layers together, contain osteoprogenitor cells

Endosteum properties

Covers inner surface of bones, contains osteoprogenitors, inactive osteoblasts

Primary bone

Initial bone produced by osteoblasts

Secondary bone

Replaces primary bone, creating uniform layers of fibers and cells to create stronger bone

Bone collar

Initial bone created by intramembranous ossification

Primary ossification center creation

BVs penetrate bone collar, osteoprogenitors produce osteoblasts, deposits primary bone onto matrix, POC in center of bone

Secondary ossification center creation

BVs invade epiphysis after birth, SOC left by ends of long bone

Bone growth after birth

Epiphyseal growth plate provides matrix for primary and secondary ossification centers until it disappears

Steps to bone remodeling

1. Osteoblasts induce monocyte fusion to make osteoclasts
2. Osteoblasts regulate osteoclasts
3. Osteoclasts create tunnel in bone, osteoblasts produce matrix
4. BVs travel into tunnel to provide nutrition

How much of the body’s total calcium is stored in bones?

more than 90%

Two hormones responsible for Ca2+ regulation

parathyroid and calcitonin

Cycle of bone fracture

1. Ruptured BVs, loss of osteocytes and bone matrix
2. Blood clot forms
3. Periosteum and endosteum proliferate, osteoblasts secrete matrix
4. CT and hyaline cartilage callus forms, replaced with primary bone via endochondral ossification
5. Bone remodeling occurs to produce secondary bone

Individual muscle cells

Myofibers (myocytes)

3 layers of protective CT in muscles

epimysium, perimysium, endomysium

Epimysium properties

Dense CT, continuous with portions of perimysium, tendons, cover entire muscle

Perimysium properties

Dense CT (thinner than epimysium), surrounds fascicles, organizes myofibers

Endomysium properties

Thin CT layer, surround each myofiber

Myofibril

cylindrical array of actin and myosin filaments, run the length of myofiber

Sarcomere

contractile unit of myofiber, split myofiber and myofibrils into sections, provide striated appearance

When do humans reach their maximum number of myofibers?

Shortly after birth

How do muscles grow?

Muscles gain length naturally until body growth stops, supported by satellite cells, additional growth as a result of exercise also a result of satellite cells, creating additional myofibrils and larger myofibers

How do muscles repair?

Satellite cells provide limited healing by dividing and fusing with myofibers

What blocks myosin binding sites on actin?

Troponin

How do muscles contract?

ATP-driven myosin heads bind to actin, pulling it towards the middle of the myosin filament

How does the motor unit (neuromuscular junction) initiate muscle contraction?

Action potential arrive at NMJ, ACh released from neuron, diffuses into sarcolemma, opens ion channels and causes depolarization, Ca gets released and allows for contraction

Two types of nervous system cells?

Neurons and glial cells

Anatomic components of NS

central (CNS) and peripheral (PNS)

Two main organs of the CNS

Brain and spinal cord

PNS function

provide sensory information from outside world, deliver commands to effectors such as muscles and glands

CNS function

integrates sensory input, produced coordinated outputs

Two functional components of NS

Somatic (voluntary) and autonomic (involuntary)

Two branches of ANS

parasympathetic and sympathetic

Dendrites

Receive and integrate incoming signals

Neurofilaments

Extend from cell body, provide support throughout neuron

Axon

Connect cell body to terminal synapses, deliver signals from cell body to synapses

Synapse

Connection of axon terminal and dendrites of next neuron

How do neurons carry signals from one another?

Transmission accomplished by changes of resting membrane potential, decrease causes depolarization, release of neurotransmitters

Bilateral

both sides

Unilateral

one side

Ipsilateral

same side (action)

Contralateral

opposite side

Three classifications of joints

Fibrous, cartilaginous, synovial

Three types of fibrous joints

suture, syndesmosis, gomphosis

What are syndesmosis joints?

interosseous membranes betwen bones

Where are syndesmosis joints present?

radius and ulna, tibia and fibula

What are the types of cartilaginous joints

primary (synchondrosis), secondary (symphysis)

What type of cartilage is used in primary cartilaginous joints?

hyaline cartilage (slight bending)

What type of cartilage is used in secondary cartilaginous joints?

fibrocartilage

Where can primary cartilaginous joints be found?

epiphyseal plates, first sternocostal joint

Where can secondary cartilaginous joints be found?

intervertebral discs, pubic symphysis

Most common joint type in the body?

synovial