Comprehensive Study Notes: The Axial and Appendicular Skeleton, Anatomical Terminology, and Body Organization

The Organ Systems

• Integumentary system

  • Major organs: Skin, Hair, Sweat glands, Nails

  • Functions: Protects against environmental hazards; helps regulate body temperature; provides sensory information

• Skeletal system

  • Major organs: Bones, Cartilages, Associated ligaments, Bone marrow

  • Functions: Provides support and protection for other tissues; stores calcium and other minerals; forms blood cells

• Muscular system

  • Major organs: Skeletal muscles and associated tendons

  • Functions: Provides movement; provides protection and support for other tissues; generates heat that maintains body temperature

• Nervous system

  • Major organs: Brain, Spinal cord, Peripheral nerves, Sense organs

  • Functions: Directs immediate responses to stimuli; coordinates or moderates activities of other organ systems; provides and interprets sensory information about external conditions

• Endocrine system

  • Major organs: Pituitary gland, Thyroid gland, Pancreas, Adrenal glands, Gonads, Endocrine tissues in other systems

  • Functions: Directs long-term changes in the activities of other organ systems; adjusts metabolic activity and energy use by the body; controls many structural and functional changes during development

• Cardiovascular system

  • Major organs: Heart, Blood, Blood vessels

  • Functions: Distributes blood cells, water, and dissolved materials including nutrients, waste products, oxygen, and carbon dioxide; distributes heat and assists in control of body temperature

• Lymphatic system

  • Major organs: Spleen, Thymus, Lymphatic vessels, Lymph nodes, Tonsils

  • Functions: Defends against infection and disease; returns tissue fluids to the bloodstream

• Respiratory system

  • Major organs: Nasal cavities, Sinuses, Larynx, Trachea, Bronchi, Lungs, Alveoli

  • Functions: Delivers air to alveoli; provides oxygen to bloodstream; removes carbon dioxide from bloodstream; produces sounds for communication

• Digestive system

  • Major organs: Teeth, Tongue, Pharynx, Esophagus, Stomach, Small intestine, Large intestine, Liver, Gallbladder, Pancreas

  • Functions: Processes and digests food; absorbs and conserves water; absorbs nutrients; stores energy reserves

• Urinary system

  • Major organs: Kidneys, Ureters, Urinary bladder, Urethra

  • Functions: Excretes waste products from the blood; controls water balance by regulating the volume of urine produced; stores urine prior to voluntary elimination; regulates blood ion concentrations and pH

• Male Reproductive system

  • Major organs: Testes, Epididymides, Ductus deferentia, Seminal vesicles, Prostate gland, Penis, Scrotum

  • Functions: Produces male sex cells (sperm), seminal fluids, and hormones; supports sexual intercourse

• Female Reproductive system

  • Major organs: Ovaries, Uterine tubes, Uterus, Vagina, Labia, Clitoris, Mammary glands

  • Functions: Produces female sex cells (oocytes) and hormones; supports developing embryo from conception to delivery; provides milk to nourish newborn; supports sexual intercourse

The Axial Skeleton

• Divisions of the skeleton

  • Axial skeleton: Bones of the head and trunk; forms the longitudinal axis of the body

  • Appendicular skeleton: Bones that support the limbs

• Bone counts (adult)

  • Total: 206 bones

  • Axial skeleton: 80 bones

  • Appendicular skeleton: 126 bones

• Components of the Axial Skeleton

  • Skull, Vertebral column, Thoracic cage (sternum and ribs)

• Skull layout (overview)

  • Cranial bones: Surround brain; include Frontal, Parietal (2), Temporal (2), Occipital, Sphenoid, Ethmoid

  • Facial bones: Support entrances to digestive/respiratory tracts; include Maxillae, Zygomatic, Nasal, Lacrimal, Inferior nasal conchae, Vomer, Palatine, Mandible

  • Associated bones: Auditory ossicles (3 per ear) within temporal bones; Hyoid bone

• Major sutures (adult skull)

  • Sagittal, Coronal, Lambdoid, Squamous

• Cranial cavity and foramina (high-level)

  • Cranial cavity houses the brain; important openings include Foramen magnum, Optic canal, Superior orbital fissure, Inferior orbital fissure, Mental foramen, etc. (refer to figure details for full list)

• Paranasal sinuses

  • Frontal, Ethmoidal, Sphenoidal, Maxillary sinuses

  • Functions: Lighten skull bones; moisten/clean air via mucus; resonating chambers in speech

• Fontanelles (infant skull)

  • Large fibrous regions that fuse over time; include anterior fontanelle, posterior fontanelle, sphenoidal fontanelle, mastoid fontanelle

• The vertebral column (overview)

  • Regions: Cervical (7), Thoracic (12), Lumbar (5), Sacral, Coccygeal

  • Primary curves: Thoracic and Sacral (present at birth)

  • Secondary curves: Cervical and Lumbar (develop after birth)

• Vertebral anatomy (typical vertebra)

  • Key parts: Vertebral body, Vertebral arch (pedicle, lamina), Spinous process, Transverse process, Superior/inferior articular processes (facets), Vertebral foramen

  • Intervertebral disc located between adjacent vertebral bodies

• Notable vertebral features by region

  • Cervical: Transverse foramina; smaller bodies; often bifid spinous process

  • Thoracic: Facets for rib articulation; smaller vertebral foramen; long spinous processes

  • Lumbar: Large, sturdy bodies; absence of costal facets; thick, blunt spinous processes

The Thoracic Cage

• Functions: Protects heart, lungs, thymus; provides attachment for muscles involved in breathing and posture

• Ribs and sternum form the rib cage

• Rib classes

  • True ribs (Ribs 1–7): Vertebrosternal; connected to sternum via costal cartilages

  • False ribs (Ribs 8–12): Vertebrochondral (8–10 fuse to 7’s cartilage); Floating ribs (11–12) do not attach to sternum

• Sternum components

  • Manubrium, Body, Xiphoid process

• Costal cartilages connect ribs to sternum

Body Cavities

• Essential functions of body cavities

  • Protect organs from shocks and allow changes in size/shape of organs

• Ventral body cavity (coelom)

  • Divided by the diaphragm into Thoracic cavity and Abdominopelvic cavity

• Serous membranes (serosa)

  • Parietal serosa lines the cavity; Visceral serosa covers the organ

• Thoracic cavity contents

  • Pleural cavities (right and left) containing the lungs

  • Mediastinum (contains vessels, trachea, esophagus, thymus)

  • Pericardial cavity (heart)

• Abdominopelvic cavity contents

  • Abdominal cavity: digestive organs; retroperitoneal space (posterior to peritoneum) includes pancreas, kidneys, ureters, parts of digestive tract

  • Pelvic cavity: reproductive organs, rectum, bladder

• Peritoneal cavity and membranes

  • Parietal peritoneum lines the internal body wall

  • Visceral peritoneum covers organs

The Appendicular Skeleton

• Overview: Bones of the limbs and girdles (limb attachments to trunk)

• Major divisions and counts

  • Pectoral girdles: 4 bones (2 clavicles, 2 scapulae)

  • Upper limbs: 60 bones each limb total 30 per limb (humerus, radius, ulna, 8 carpals, 5 metacarpals, 14 phalanges per limb) → 60 per limb; both limbs 120 total

  • Pelvic girdle: 2 hip bones

  • Lower limbs: 60 bones per limb (femur, patella, tibia, fibula, 7 tarsals, 5 metatarsals, 14 phalanges per foot) → 60 per limb; both limbs 120 total

• Overall appendicular total: 126 bones

• Bones of the upper limb (examples and landmarks)

  • Clavicle: acromial end (lateral), sternal end (medial); conoid tubercle

  • Scapula: acromion, coracoid process; spine; glenoid cavity

  • Humerus: head, anatomical neck, surgical neck, greater/lesser tubercles, deltoid tuberosity, trochlea, capitulum

  • Radius and Ulna: proximal radioulnar joint; interosseous membrane; styloid processes

  • Carpals: proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate)

  • Metacarpals and Phalanges: metacarpals I–V; proximal/middle/distal phalanges

• Bones of the lower limb (highlights)

  • Femur: head, neck, greater/lesser trochanters, linea aspera, condyles

  • Patella: base and apex; articular facets

  • Tibia and Fibula: proximal/distal ends; tibial tuberosity; medial/lateral malleoli

  • Tarsals: talus, calcaneus, navicular, cuboid, cuneiforms (medial, intermediate, lateral)

  • Metatarsals and Phalanges: similarly organized to the hand

• Pelvis and lower limb articulation

  • Hip bone comprised of ilium, ischium, pubis; acetabulum; pelvic girdle supports weight transfer to lower limbs

Facial Bones, Orbital/Nasal Complexes, and Related Structures

• Facial bones provide entrance protection to digestive/respiratory tracts and shape the face

• Orbit and nasal complexes include detailed structures (example highlights):

  • Orbits formed by frontal, zygomatic, maxilla, sphenoid, ethmoid, lacrimal, palatine, and nasal bones

• Hyoid bone

  • Supports the larynx; attaches muscles of the tongue, pharynx, and larynx

• Auditory ossicles

  • Three tiny bones in the middle ear (malleus, incus, stapes) per ear; transfer sound from tympanic membrane to inner ear

Sectional Anatomy and Planes (Key Concepts)

• Section: a slice through a three-dimensional object; used to visualize internal organization

• Sectional plane definitions

  • Frontal (coronal) plane: divides body into anterior and posterior portions; cut yields frontal (coronal) section

  • Sagittal plane: divides body into left and right portions; midsagittal plane passes through the midline; parasagittal plane is offset from the midline

  • Transverse (horizontal) plane: divides body into superior and inferior portions

• Directional terms (examples)

  • Superior (cranial/cephalic): toward the head

  • Inferior (caudal): toward the feet

  • Anterior (ventral): toward the front; Posterior (dorsal): toward the back

  • Medial: toward the midline; Lateral: away from the midline

  • Proximal: closer to the point of limb attachment; Distal: farther from attachment

  • Superficial: at/near the surface; Deep: farther from the surface

• Anterior view examples

  • The head is superior to the chest; The shoulder is proximal to the wrist; The knee is distal to the hip

Abdominopelvic Quadrants and Regions

• Abdominopelvic quadrants

  • Right Upper Quadrant (RUQ)

  • Left Upper Quadrant (LUQ)

  • Right Lower Quadrant (RLQ)

  • Left Lower Quadrant (LLQ)

• Abdominopelvic regions (from the diagrams)

  • Right hypochondriac, Epigastric, Left hypochondriac

  • Right lumbar, Umbilical, Left lumbar

  • Right inguinal, Hypogastric (pubic), Left inguinal

Sectional References and Organ Relationships

• Frontal, sagittal, transverse sections are used to study relationships among organs and cavities

• The skull’s floor and cranial cavity orientation is important for clinical imaging (e.g., diagnostic CT/MRI conventions)

The Vertebral Column: Regions and Structure

• Regions by vertebrae

  • Cervical (7), Thoracic (12), Lumbar (5), Sacral, Coccygeal

• Primary vs secondary curves

  • Primary: thoracic and sacral (kyphosis)

  • Secondary: cervical and lumbar (lordosis)

• Vertebral anatomy (typical vertebra)

  • Vertebral body; Vertebral arch (pedicle, lamina); Spinous process; Transverse process; Superior/inferior articular processes and facets; Vertebral foramen

• Functional notes

  • The curves help balance the trunk over the lower limbs; some curves develop with standing and walking

The Thoracic Cage: Ribs and Sternum

• Ribs

  • True ribs (1–7): vertebrosternal; connected to sternum by costal cartilages

  • False ribs (8–12): vertebrochondral (8–10 fuse with cartilage of rib 7); Floating ribs (11–12) have no anterior attachment

• Sternum components

  • Manubrium, Body, Xiphoid process

• Costal cartilages connect ribs to sternum

Paranasal Sinuses and Orbital/Nasal Complexes

• Paranasal sinuses provide reduction in skull weight; mucus production; resonance for voice

• Major sinus groups: frontal, ethmoid, sphenoidal, maxillary

Fontanelles (Infant Skull)

• Large fibrous regions where sutures are not yet fused

• Allow skull flexibility during birth and rapid brain growth after birth

• Major fontanelles include anterior and posterior (and sphenoidal/mastoid in some diagrams)

The Lower Limbs and the Skeleton of the Foot and Ankle

• Key components (overview): femur, patella, tibia, fibula, tarsals (calcaneus, talus, navicular, cuboid, cuneiforms), metatarsals, phalanges

• Notable markings and joints on the femur, tibia, fibula, and foot bones are used for muscle attachments and articulation

Individual Skeletal Variation

• Skeletal features can reveal:

  • Muscle strength and mass (bone ridges, bone mass)

  • Medical history (tooth condition, healed fractures)

  • Sex and age (bone measurements and fusion)

  • Body size

• Sex differences in the skeleton (high-level summary from Fig. 8-14)

  • Skull: male vs female differences in size and shape; males generally larger and more robust; females tend to have smoother features

  • Pelvis: females have wider pelvic inlet and outlet to accommodate childbirth; pelvic anatomy differs to allow or limit birth canal size; pubic angle tends to be larger

• Hormonal influence on pelvis during pregnancy

  • Hormone relaxin loosens pubic symphysis and sacroiliac ligaments; increases pelvic inlet and outlet size to facilitate birth

Notation of Numeric and Structural Details (quick reference)

• Adult skeleton bone counts

  • Total = 206

  • Axial = 80

  • Appendicular = 126

• Skull bone counts (overview)

  • Cranium: 8 bones

  • Facial bones: 14 bones

  • Auditory ossicles: 6 bones (3 per ear)

  • Hyoid: 1 bone

• Vertebral column counts by region

  • Cervical: 7

  • Thoracic: 12

  • Lumbar: 5

• Thoracic cage components

  • Ribs: 12 pairs; True ribs: 7 pairs; False ribs: 3 pairs; Floating ribs: 2 pairs

  • Sternum: Manubrium, Body, Xiphoid process

• Appendicular skeleton totals (per girdle/limbs)

  • Pectoral girdles: 4 bones total

  • Upper limbs: 60 bones

  • Pelvic girdle: 2 bones

  • Lower limbs: 60 bones

• Percent and relative observations (as described in the sex-differences figures)

  • Overall skeletal differences between sexes are reflected in size, robustness, and pelvic morphology; exact percentages vary by trait across the sources, with broader pelvic differences facilitating childbirth in females

Quick References to Figures (where to look in the transcript)

• Figure 7–1: The Axial Skeleton (bone counts and layout)

• Figures 7–2, 7–3: Cranial and facial subdivisions; skull sutures; major bones

• Figure 7–4: Sectional anatomy of the skull (cranial cavity and floor)

• Figure 7–6 to 7–7: Frontal bone and temporal bones (landmarks and notable openings)

• Figure 7–9 to 7–10: Ethmoid, Maxillae, Palatine bones (nasal/orbital relationships)

• Figure 7–12 to 7–16: Mandible, hyoid, fontanelles, and infant skull features

• Figure 7–17 to 7–18: Vertebral anatomy and sectional views

• Figures 7–19 to 7–21: Cervical, Thoracic, and Lumbar vertebrae details

• Figures 7–22 to 7–23: Sacrum and Coccyx, and transverse sections of the trunk cavities

• Figures 7–24: Ribs and their articulations

• Figures 8–1 to 8–13: Appendicular skeleton (clavicle, scapula, humerus, radius/ulna, carpal/metacarpal/phalanges, pelvis, femur, patella, tibia/fibula, tarsals, metatarsals, phalanges)

• Figures 8–14: Sex differences in the skeleton (overview of skull, pelvis, and general features)

• Figure 8–16 (and related): Infant skull fontanelles and infant skull anatomy

*** Notes on LaTeX formatting used in this document: all numerical references and counts are indicated with LaTeX syntax, enclosed in double dollar signs, for example: 206, 80, 126, 7, 12, 5, etc. This makes numerical anchors consistent for exam review. If you need a version without LaTeX formatting, tell me and I can provide a clean, plain-number variant. ***