DSF wk 1 obj

Question 1

Define components of the skeletal system, including major supportive structures

Answer 1

206 bones
Living CT
Vascular and innervated
Functions: Support, protection, storage, mechanical basis for movement, blood cell production 
Cartilage: Avascular

Question 2

Describe the classification of bones and their features/markings

Answer 2

All bones has superficial thin layer of cortical bone (strength; weight-bearing) around a central mass of spongy bone
Some have medullary (marrow) cavity
Classified according to shape: long, short, flat, irregular, sesamoid (protect tendons from excessive wear, often change angle of tendons as they pass to attachments)
Periosteum: external, fibrous CT, tough and highly vascular, helps anchor muscles to bone, reacts to trauma
Endosteum: internal, ill-defined largely cellular membrane

Question 3

Describe parts of the axial and appendicular skeleton

Answer 3

Axial: Midline structures of skeleton - bones of head, neck, trunk
Appendicular: Bones of the arms, legs, pelvic and pectoral girdles (all paired)

Question 4

Describe organization of the NS into anatomic divisions (CNS, PNS) and functional divisions (somatic, autonomic)

Answer 4

CNS: brain and spinal cord
PNS: cranial nerves (12 pairs), spinal nerves (31 pairs), autonomic nerves
Somatic NS: voluntary. Sensory inputs from skin surface, skeletal muscle, bone, tendon, joints. Motor outputs to skeletal muscles
Autonomic NS: Visceral - involuntary. Sensory inputs from viscera and blood vessels (autonomic reflexes, pain signals from viscera). Motor output to cardiac muscle, glands, smooth muscle in walls of organs and vessels.
ANS subdivisions - Sympathetic (fight or flight) and Parasympathetic (rest and digest).
Somatic and Autonomic both contain sensory (afferent) fibers and motor (efferent) fibers

Question 5

Describe the structure of typical neurons, the different functional types and their targets for innervation

Answer 5

See diagram on slides for structures
Oligodendrocytes: glial cells of CNS
Schwann cells: glial cells of PNS

Question 6

Describe the gross anatomy of the spinal cord and its anatomic relations to vertebrae

Answer 6

(Except in upper cervical spinal cord) the vertebral body closest to a spinal cord segment is at least 1 level higher, and often many more (ex: lumbar cord: T10-T12 vertebrae)

Question 7

Discuss how spinal nerves and spinal cord segments are named and numbered

Answer 7

31 pairs of spinal nerves: named for section of spinal cord from which they arise
8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
In cervical spinal cord: spinal nerves exit above the corresponding vertebra
Rest of spinal cord: spinal nerves exit below the corresponding vertebrae
Spinal nerves exit vertebral column via intervertebral foramen

Question 8

Draw and label a cross-section of the spinal cord including dorsal and ventral horns, gray and white matter, dorsal and ventral roots, DRG, spinal nerve, dorsal and ventral rami

Answer 8

Draw out
A spinal cord segment is comprised of a pair of spinal nerves
Nerve rootlets from the spinal cord converge to form 2 roots: Anterior (contains motor fibers whose cell bodies are in spinal cord gray matter - anterior and lateral horns) and Posterior (contains sensory fibers whose cell bodies located in spinal ganglion, DRG, outside of spinal cord)
Anterior and posterior roots unite to form a spinal nerve, which contains both motor and sensory fibers
Spinal nerve immediately divides into Anterior ramus and Posterior ramus
Anterior ramus: innervates muscles of anterior and lateral trunk, upper and lower limbs and overlying skin (stay as separate nerves to innervate trunk - intercostal nerves, form plexus to supply limbs)
Posterior ramus: innervates joints of the vertebral column, deep muscles of the back, and overlying skin (stay as separate nerves)

Question 9

Draw the pathway and fiber content of a typical intercostal nerve

Answer 9

Sensory receptors - pseudounipolar sensory neuron - DRG - posterior root of spinal nerve
Anterior root of spinal nerve - somatic multipolar motor neuron - effector organ (skeletal muscle)
Anterior root of spinal nerve - presynaptic and postsynaptic autonomic multipolar motor neurons (synapse w/in autonomic ganglion) - synapse on glands/cardiac muscle/smooth (involuntary) muscle of organs

Question 10

Define the concept of a dermatome and its relationship w/ a spinal cord segment (segmental innervation)

Answer 10

Each spinal cord segment has somatic and autonomic components
Dermatome: map of segmental sensory innervation
Each spinal cord segment is responsible for cutaneous innervation of a particular region
C1-C8: dorsal head, neck, shoulders, arms, hands
T1-T12: anterior trunk and abd, medial arms
L1-L5: posterior lower back, anterior and lateral legs, soles of feet
S1-S5: genitals, posterior legs

Question 11

Describe in general terms, the structure of the vertebral column and the components of a typical vertebra

Answer 11

See diagrams on slides

Question 12

Define the primary and secondary curvatures of the spine and differentiate b/w abnormal curvatures

Answer 12

Primary curvatures: Sacral, Thoracic - form during fetal development
Secondary curvatures: Lumbar, Cervical - develop after birth (from walking and lifting head, respectively)
Kyphosis - can be caused by compression fxs (elderly) - outward rounding of upper back, “hunchback”
Lordosis - excessive inward curve of the spine
Scoliosis - sideways curvature of the spine

Question 13

Describe the location and function of the intervertebral discs and major supporting ligaments of the spinal column

Answer 13

Intervertebral discs: connect adj vertebrae, shock absorption
Disc reinforced by anterior and posterior longitudinal ligaments
Disc herniation most often occurs in posterolateral region - annulus fibrosus is thinner and has fewer lamellar in posterior aspect
Ligaments connecting adj vertebrae: resist hyperflexion

Question 14

Define and list examples of extrinsic and intrinsic back muscles

Answer 14

Intrinsic: Deep muscles (Splenius-capitis and cervicus, Erector spinae-Spinalis, Longissimus, Iliocostalis, Transversospinales-Semispinalis capitis, Multifidus, Rotatores)
Extrinsic: Intermediate (Serratus posterior superior and inferior - Respiratory) and Superficial (Trapezius, Latissimus dorsi, Rhomboid major and minor, Levator scapulae - Appendicular)

Question 15

Describe the location, function, and innervation of the superficial (appendicular), intermediate (respiratory), and deep (intrinsic) back muscles

Answer 15

x

Question 16

Describe the pattern of arterial supply and venous return within the back

Answer 16

x

Question 17

Review the gross anatomy of the spinal cord and supporting meningeal structures

Answer 17

Meningeal spaces of the brain and spinal cord are continuous w/ one another
Dura mater, archnoid mater, pia mater
Pia mater: Denticulate ligaments (attach spinal cord to superficial meningeal layers) and Filium terminale (connects spinal cord to coccyx, provides tension to stabilize spinal cord)

Question 18

Formulate the stages of prenatal development with emphasis on their relative vulnerability to teratogens.

Answer 18

0-2 wks Germinal period: not sensitive usually, high rate of lethality can occur
3-8 wks Embryonic period: period of greatest sensitivity, each organ system will also have a peak sensitivity
9-38 wks Fetal period: decreasing sensitivity, period of functional maturation

Question 19

Compare and contrast b/w embryonic/fertilization and gestational/menstrual age.

Answer 19

During a regular menstrual cycle, ovulation occurs at day 14. Assuming fertilization to occur ~during same time, embryo is already 2 wks old when the mother misses her next period.
Gestational (menstrual) age [counted from the 1st day of the LMP] is always 2 wks greater than the embryonic (fertilization, counted from day of fertilization) age.

Question 20

Construct the development of the embryo from a zygote to a blastocyst.

Answer 20

W/in 24 hrs zygote formation, embryo undergoes series mitotic divisions (cleavage) in which the cell #s increase at expense of size (no cytoplasm synthesis) - loosely packed, increasingly smaller cells - blastomeres.
~3 days after fertilization, embryo divides to form a 16-cell morula, that enters uterine cavity.
Morula eventually differentiates into a blastocyst, in which cells organize into an inner (embryoblast) and outer (trophoblast) cell mass.
Embryoblast - embryo
Trophoblast - placenta

Question 21

Illustrate the stages, duration, and molecular regulation of the preimplantation phase.

Answer 21

Degeneration of zona pellucida
Adplantation - Initial adhesion of blastocyst to uterine epithelium - slows in motility, “rolls” on surface, aligns w/ the inner cell mass closest to the epithelium, and, stops
Initial attachment mediated by L-selectin on trophoblast cells and its carbohydrate receptors on the uterine epithelium

Question 22

Critique the microstructure of the uterine endometrium and the phase of the menstrual cycle at implantation.

Answer 22

~Days 6/7-13: blastocyst implantation
Occurs in the functional (compact) layer of the endometrium during the secretory phase of the ovarian cycle
Decidua: specialized, highly modified endometrium of pregnancy.
Transformation of endometrial stromal cells, occurring initially at site of implantation: become polyhedral, loaded w/ glycogen and lipids, intercellular spaces filled w/ extravasate.
Decidualization: transformation of secretory endometrium to decidua, dependent on estrogen and progesterone and factors secreted by the implanting blastocyst.

Question 23

Outline the normal types of implantation and predict the clinical outcomes of extra-uterine pregnancies.

Answer 23

Normal: Implantation hemorrhage - varies in amount/duration/character from regular menstrual bleeding - around days 13-14 (days 27-28 of menstrual cycle)
Cells of syncytiotrophoblasts erode through endothelial lining of maternal capillaries
Ectopic pregnancy: (extra-uterine implantation) most common in the uterine tube. Can be caused by PID. Ruptured tubal pregnancy is surgical emergency - hemorrhage
Mother presents during 1st trimester w/: abd pain, vaginal bleeding, signs of internal hemorrhage/shock (hypotension, tachycardia, rapid and feeble pulse)

Question 24

Design the development of the bilaminar germ disk, amnion, chorion, amniotic and chorionic cavities, and the yolk sac during the 2nd week of embryonic development.

Answer 24

Day 8: Trophoblast differentiates into cytotrophoblast and syncytiotrophoblast (secrete hCG: maintain decidua and corpus luteum)…Embryoblast differentiates into epiblast and hypoblast
Day 9: At embryonic pole, vacuoles appear in synctium and fuse, forming Trophoblastic lacunae. Flattened cells from hypoblast form thin exocelomic membrane - Heuser’s Membrane - lines exocoelomic cavity, primitive yolk sac. Cavity formed w/in cells of epiblast - Amniotic cavity.
Days 11-12: new cells derived from yolk sac appear b/w cytotrophoblast and Heuser’s membrane - extra-embryonic mesoderm…cavities develop w/in newly formed mesoderm; coalesce to form extra-embryonic coelom - Chorionic cavity.

Question 25

Design the process of gastrulation w/ emphasis on the morphogenetic role of the primitive streak in forming the trilaminar embryo.

Answer 25

Gastrulation: 3rd wk - process that establishes the 3 definitive germ layers of the embryo (ectoderm, intra-embryonic mesoderm, endoderm), forming a trilaminar embryonic disk Primitive streak forms day 15, caused by proliferation of epiblast cells.

Question 26

Predict the consequences of ineffective gastrulation (caudal dysgenesis) and failure of regression of the primitive streak (sacrococcygeal teratoma).

Answer 26

Caudal dysgenesis: occurs if gastrulation stops too soon - head and thoracic regions of embryo are well developed, but insufficient cells available to form normal pelvis, GU organs, and lower limbs. Death usuallu from defective kidney formation. Rare but mostly observed in fetuses of diabetic mothers. Sacrococcygeal teratoma: Common congenital germ cell tumor, develops from abnormal remnants of primitive streak. Tumor consists of derivatives of all 3 germ layers. Polyhydramnios common b/c increased fetal CO - often preterm labor and premature membrane rupture. Severe cases - Maternal Mirror Syndrome - mother develops HTN, hyperemesis, pulmonary edema, proteinuria.

Question 27

Critique the formation of the notochord and its role in the differentiation of nerve tissue.

Answer 27

Some mesenchymal cells that have ingressed through the primitive streak migrate cranially from the primitive node and pit, forming a median cellular cord, the notochordal process - which grows cranially b/w the ectoderm and endoderm until it reaches the prechordal plate. As differentiation continues, the cells of the notochord plate detach from the hypoblast and form a continuous line of cells called the notochord - critical for establishing the midline and axis of embryo - important signaling center for inducing axial skeleton. Eventually forms the nucleus pulposus of each intervertebral disc.

Question 28

Discuss the fate of the notochord in adult human being and predict consequences of its incomplete involution (chordoma).

Answer 28

Chordomas: malignant neoplasms from cellular remnants of the notochord . Frequently affects sacrum - rare, slow-growing, primary bone tumor. Notochord eventually forms the nucleus pulposus of each intervertebral disc.

Question 29

Formulate the stages of neurlation and the initial steps in the genesis of the CNS and PNS.

Answer 29

Notochord and prechordal plate induce the overlying ectoderm to thicken and form neural plate - initiation of Neurulation. Occurs in cranial-to-caudal sequence. Neural folds - elevated lateral edges of neural plate - fuse to form neural tube.

Question 30

Design the genesis of the neural crest cells and outlines its derivatives.

Answer 30

Neural crest cells originate from edges (crests) of neural folds as neurulation proceeds. Form along entire length of neural tube in neuroectoderm cells. Migrate away from neural tube to form many different tissues - PNS, Pia and Arachnoid mater, CT, dermis, some bones of head and neck, melanocytes, cardiac septa, medulla of adrenal gland, parafollicular cells of thyroid Neural crest cells are incredibly sensitive to insults from teratogens.

Question 31

Critique the differentiation and derivatives of intra-embryonic mesoderm.

Answer 31

Mesoderm differentiates into 3 parts: paraxial mesoderm along neural tube axis that forms somites; intermediate mesoderm that forms the gonads and parts of the UG system; lateral plate mesoderm that will line body cavities. Lateral plate mesoderm splits into 2 layers: visceral (splanchic) and parietal (somatic). Visceral mesoderm associated w/ organs, parietal mesoderm associated w/ body wall. Space b/w these layers (intraembryonic coelom) constitutes the body cavity.

Question 32

Correlate the microscopic structure of skin w/ its functions.

Answer 32

x

Question 33

Correlate the histological layers and cell types of epidermis with their functions.

Answer 33

x

Question 34

Analyze the transformation of keratinocytes from the basal to superficial layers, ultimately resulting in keratinization.

Answer 34

x

Question 35

Describe the process of melanin synthesis and donation by melanocytes.

Answer 35

Melanocytes originate from neural crest. Melanin synthesized by melanocytes in Stratum basale. Melanin produced by oxidation of Tyr (Tyrosinase key) and packaged in melanosomes. Keratinocytes take up melanin by cytocrine secretion: they phagocytose the tips of dendritic processes. Most melanin is found in keratinocytes. Melanin found above nucleus of basal cells - protecting DNA from radiation. Skin pigmentation determined by amount, type, packaging of melanin in epidermis - melanin breakdown rate (faster in lighter-skinned individuals).

Question 36

Correlate the histological organization and cell types of the following epidermal derivatives with their locations and functions: sebaceous glands, eccrine sweat glands, apocrine sweat glands.

Answer 36

x

Question 37

Correlate the microstructure of the sensory receptors in the skin w/ their locations and functions.

Answer 37

x

Question 38

Compare thick and thin skin in terms of histological organization, distribution of epidermal derivatives, locations, and functions.

Answer 38

x

Question 39

Correlate underlying defects in the following disease processes that result from structural and functional alterations of skin: psoriasis, albinism, diabetic neuropathy, vitiligo.

Answer 39

x

Question 40

Describe normal dev of integumentary system (including skin appendages) w/ primary focus on: Epidermal layers and cells, keratinization, hair, mammary glands

Answer 40

x

Question 41

Identify common birth defects of integumentary system

Answer 41

Congenital bulbous disorders (EBS, JEB, DEB) Icythyosis (IV, LI, Harlequin. XLR) Hypopigmentation disorders (OCA, Waardenburg's syndrome, Piebaldism) Hypohidrotic ectodermal dysplasia

Question 42

Congenital bulbous disorders (EBS, JEB, DEB)

Answer 42

x

Question 43

Icythyosis (IV, LI, Harlequin. XLR)

Answer 43

x

Question 44

Hypopigmentation disorders (OCA, Waardenburg's syndrome, Piebaldism)

Answer 44

x

Question 45

Hypohidrotic ectodermal dysplasia

Answer 45

x

Question 46

Describe classification of joints and identify examples of each

Answer 46

x

Question 47

Describe components of a synovial joint

Answer 47

x

Question 48

Discuss the different types of synovial joints and the movements they permit

Answer 48

x

Question 49

Discuss the importance of peri-articular synovial structures: bursae and tendon sheaths.

Answer 49

x

Question 50

Identify types of musculoskeletal injuries

Answer 50

x

Question 51

Identify bones of the shoulder region and major features including muscle attachment sites and articular surfaces

Answer 51

Scapula Clavicle Proximal Humerus

Question 52

Describe the movements permitted by the shoulder joint (glenohumeral joint)

Answer 52

x

Question 53

Describe the attachments, actions, innervations of the rotator cuff, pectoral and posterior shoulder muscles

Answer 53

x

Question 54

Describe the anatomic structures (ligaments, cartilage, capsule) which act as static stabilizers and dynamic constraints of the shoulder

Answer 54

x

Question 55

Correlate the clinical presentation of disorders of the shoulder region w/ structural and functional alterations

Answer 55

x

Question 56

Describe the blood supply and venous drainage of the shoulder region including the vessels providing collateral circulation in the scapular anastomosis

Answer 56

x

Question 57

Describe the organization of the brachial plexus in terms of roots, trunks, divisions, cords, major branches.

Answer 57

5 roots: anterior rami of spinal nerves C5, C6, C7, C8, T1 3 trunks: upper (C5+C6), middle (C7), lower (C8, T1) 6 divisions: (anterior + posterior) 3 cords: Lateral (C5-C7 *anterior), Medial (C8-T1 *anterior), Posterior (C5-T1) 5 major branches: Musculocutaneous n. C5-C7 (*anterior), Median n. C6-T1 (*anterior), Ulnar n. C8-T1 (*anterior), Axillary n. C5-C6 (*posterior), Radial n. C5-T1 (*posterior)

Question 58

Describe the spatial relationship of the parts of the brachial plexus to the cervical region and axilla

Answer 58

Spinal nerves C5-T1 come from intervertebral foramina, go through interscalene groove (b/w anterior and middle scalene muscles) and costoclavicular space (b/w clavicle and 1st rib), go through axilla, to innervate upper limb Supraclavicular portion: 5 roots, 3 trunks, 6 divisions Infraclavicular portion: 3 cords, 5 major branches

Question 59

Describe the motor and sensory functions of the branches of the brachial plexus

Answer 59

Musculocutaneous n. C5-C7 (from medial and lateral cords): Anterior arm muscles (coracobrachialis, biceps brachii, brachialis), skin of lateral forearm Median n. C6-T1 (from medial and lateral cords): Most anterior forearm muscles, most thenar muscles, 2 lumbricals (intrinsic hand), skin of palm, 1-3 digits, 1/2 of 4th digit Ulnar n. C8-T1 (from medial and lateral cords): 1/2 anterior forearm muscles (flexor carpi ulnaris, flexor digitorum profundus, most intrinsic hand muscles, skin of medial hands, 5th digit, 1/2 of 4th digit Axillary n. C5-C6 (from posterior cord): Deltoid and teres minor, skin of lower deltoid region Radial n. C5-T1 (from posterior cord): Muscles of posterior arm and posterior forearm, skin of posterior forearm, dorsum of hand, dorsum of most digits)

Question 60

Describe the course of the 5 major branches (musculocutaneous, median, ulnar, axillary, radial nerve) , noting their relationships to joints and muscles

Answer 60

Draw out

Question 61

Explain the distribution of dermatomes on the upper limb

Answer 61

x

Question 62

Identify sites where parts of the brachial plexus are vulnerable and prone to injury

Answer 62

Surgical neck of humerus - Axillary n. Radial groove (mid-shaft) of humerus - Radial n. Medical epicondyle of humerus (Ulnar n.

Question 63

Describe the structure of the breast

Answer 63

Parenchyma: mammary glands - modified sweat glands Stroma: fibrous tissue and adipose tissue Held together by suspensory ligaments (mostly located superior) that attach to overlying dermis

Question 64

Describe the position of the breast in relation to skin, superficial fascia and pectoral muscles

Answer 64

``` Breast = subcutaneous organ, located directly beneath the skin Overlies pectoralis major fascia Retromammary space (potential space) ```

Question 65

Discuss the lymphatic drainage of the breast and its significance in the spread of CA

Answer 65

75% of breast drainage is to lymph nodes of axilla Remaining 25% drains to nodes along sternum or to opposite breast Axillary nodes also drain upper limb

Question 66

Describe the blood supply, venous drainage and innervation of the breast

Answer 66

Venous blood drains primarily to the axillary vein, but also to the internal thoracic vein Innervated by 4th-6th intercostal nerves Blood supply from Anterior intercostal a. (branch of Subclavian a.), Thoracoacromial trunk (branch of Axillary a.), and Lateral thoracic a. (branch of Axillary a.)

Question 67

Describe the location, boundaries, and general contents of the axilla

Answer 67

4-sided pyramidal space, inferior to the glenohumeral joint and superior to the axillary fascia at the junction of the arm and thorax Apex (formed by cervicoaxillary/costoclavicular space), base/floor (axillary fascia and skin b/w upper arm and lateral thoracic wall), 4 walls (anterior, posterior, medial, lateral) Contents: Fat, axillary sheath, axillary artery and branches, axillary vein and tributaries, cords and terminal nerves of Brachial plexus, axillary lymph nodes

Question 68

Describe the course and major branches of the axillary artery

Answer 68

Axillary artery begins at the lateral border of the 1st rib as continuation of the Subclavian artery Axillary a. ends at inferior border of the teres major as the Brachial a. Axillary a. divides into 3 parts: Proximal, Middle, Distal Branches: Proximal - Superior thoracic a. (supplies muscles of 1st intercostal space) Middle - Thoracoacromial a. (deltoid, pectoral, clavicular, acromial branches) and lateral thoracic a. (supplies the lateral thoracic wall, including the serratus anterior and the breast) Distal - subscapular a. (provides Thoracodorsal a. supplying latissimus dorsi and circumflex scapular a. supplying muscles of the scapula), anterior and posterior circumflex humeral a. (both encircle humeral neck to supply deltoid region)

Question 69

Describe the superficial and deep venous drainage of the upper extremity, including the course of the axillary, basilic and cephalic veins

Answer 69

Axillary vein begins at the inferior border of teres major Contributions from: lateral chest wall and thoracoepigastric vein Axillary vein divides into 3 parts Brachial veins - deep Cephalic and basilic veins - superficial

Question 70

Describe the lymphatic drainage pattern to axillary lymph nodes

Answer 70

Lymphatic vessels of the upper limb drain toward the axilla, usually accompany the superficial veins (cephalic and basilic) Embedded in axillary fat, external to sheath 5 principal groups Nodes of lower axillary group (pectoral, subscapular, humeral) drain to the central nodes - drains to apical nodes (along w/ other lymphatic vessels) - unite to form subclavian lymph trunks Excision of axillary lymph nodes often necessary for staging - this removal may impede lymphatic drainage, resulting in lymphedema

Question 71

Brachial Plexus

Answer 71

Somatic nerve plexus formed by the anterior rami of cervical spinal nerves C5-C8 and thoracic spinal nerve T1 Provides motor and sensory innervation for muscles, skin and joints of the upper limb

Question 72

List common Imaging Modalities used to evaluate clinical anatomy and physiology

Answer 72

``` Radiographs (x-rays) Fluoroscopy Angiography CT MRI Ultrasound Nuclear imaging/PET ```

Question 73

Explain basic process of how x-rays create an image of internal body structures

Answer 73

When x-ray meets body, x-ray can be: deflected/scattered, absorbed, pass through X-rays passing through tissue produces the 2D image X-rays that pass through the body to the detector - dark (BLACK) *Ex: air, low atomic # X-rays that are totally blocked do not reach the detector - light (WHITE) *Ex: metal, high atomic #

Question 74

Identify and describe the 5 basic radiographic densities

Answer 74

``` Metal: Absorbs nearly all x-rays - WHITE Calcium: Bone - NEARLY WHITE Soft tissue: Fluid and soft tissue (equal) - GRAY Fat - DARK GRAY Air: absorbs the least x-ray - BLACK ```

Question 75

Describe and contrast: Radiographs, CT, MRI, Ultrasound

Answer 75

Radiographs: Electromagnetic energy (x-rays) no charge, no mass. Ionizing radiation. Primary/initial modality for acute pulmonary disease, many abd. complaints, skeletal abnormalities/injuries. When x-ray meets body, x-ray can be: deflected/scattered, absorbed, pass through - produces 2D image. CT: Gantry w/ rotating x-ray beam and detector. Ionizing radiation. Connected to computer that processes data to produce slice-like images. HU densities: air least, bone most dense. MRI: Images produced using a high-field strength magnet and radio-frequency signals. No ionizing radiation. Ultrasound: Images created using reflected sound waves. No ionizing radiation. No harmful effects. Highly operator dependent. Grayscale and Doppler Imaging - can directly assess blood flow and vascular patency. Echogenic (white) vs. anachoic (black) ~ echoes.