Human Anatomy Study Guide

Four types of Bones

Long, Short, Flat, Irregular

Long Bones

Longer than they are wide (e.g., femur, humerus)

Short bones:

Cube-like, with nearly equal length, width, and thickness (e.g., carpals, tarsals)

Flat bones:

Thin, flattened, and usually curved (e.g., sternum, ribs, skull bones)

Irregular bones:

Complex shapes that don’t fit into the other categories (e.g., vertebrae, pelvic bones)

Functions of Bone

Support, Protection, Movement, Mineral Storage, Blood Cell Production, Energy Storage

Support:

Bones form the framework that supports the body.

Protection:

Bones protect vital organs (e.g., skull for brain, ribs for heart and lungs)

Movement:

Bones serve as levers for muscles to produce movement.

Mineral Storage:

Bones store minerals such as calcium and phosphorus.

Blood Cell Production:

Bone marrow produces red and white blood cells and platelets.

Energy Storage:

Bones store lipids in adipocytes of yellow marrow for energy reserves.

Bone Cell Types

Osteoblasts Osteocytes, Osteoclasts, Osteoprogenitor Cells

Osteoblasts:

Bone-forming cells.

Osteocytes:

Mature bone cells that maintain bone tissue

Osteoclasts:

Cells that break down bone tissue for remodeling and calcium release.

Osteoprogenitor cells:

Stem cells that develop into osteoblasts.

Factors affecting bone development and growth

Nutrition Hormones, Physical Activity, Genetics

Nutrition:

Involves an adequate intake of calcium, vitamin D, and phosphorus.

Hormones:

Growth hormone, thyroid hormones, and sex hormones influence bone growth.

Physical Activity:

Weight-bearing exercises stimulate bone growth and strength.

Genetics:

Genetic factors determine bone density and growth patterns

Endochondral Ossification

is the process by which bone forms from a cartilage model.

Steps of Endochondral Ossification

1. Development of the cartilage model

2. Growth of the cartilage model

3. Primary ossification center

4. Development of the medullary cavity

5. Secondary ossification centers

6. Formation of articular cartilage and epiphyseal plate

Development of the cartilage model:

Mesenchymal cells develop into chondroblasts, which form hyaline cartilage.

Growth of the cartilage model:

The cartilage model grows and begins to calcify

Primary ossification center:

Blood vessels infiltrate the cartilage and osteoblasts begin to form bone in the diaphysis (shaft)

Development of the medullary cavity:

Osteoclasts break down the newly formed bone to create the cavity.

Secondary ossification centers:

These form in the epiphyses (ends) of the bone.

Formation of articular cartilage and epiphyseal plate:

Articular cartilage remains on the joint surfaces, and the epiphyseal plate (growth plate) remains between the diaphysis and epiphysis

epiphyseal plate aka

growth plate

Types of Fractures

Comminuted, Spiral, Greenstick, Transverse, Oblique, Compression, Stress, Pathological

Comminuted Fracture:

The bone is broken into several pieces

Spiral Fracture

A twisting or rotational force causes a fracture that spirals around the bone

Greenstick Fractures

An incomplete fracture, often in children, where one side of the bone is bent while the other side is broken.

Transverse Fracture

A straight across fracture at a right angle to the bone’s long axis

Oblique Fractures

A diagonal fracture that is not parallel to the bone’s axis

Compression Fracture

Bone is crushed, often occurring in porous bone (e.g., vertebrae).

Stress Fracture:

A small crack in the bone caused by repeated stress or overuse

Pathological Fracture:

A fracture that occurs in a bone weakened by disease (e.g., osteoporosis, cancer)

Structure of Long Bone

Diaphysis, Epiphysis, Epiphyseal, Medullary Cavity, Endosteum, Periosteum, Articular Cartilage

Diaphysis

The shaft of the long bone, made of compact bone that provides strength

Epiphysis:

The ends of the bone, which are usually spongy and contain red bone marrow.

Epiphyseal Plate (Growth Plate):

A hyaline cartilage plate that allows for bone growth in length.

Medullary Cavity:

Hollow center of the diaphysis, which contains yellow bone marrow.

Endosteum:

Membrane lining the medullary cavity and bone surfaces.

Periosteum:

A dense layer of vascular connective tissue surrounding the bone except at the joints.

Articular Cartilage:

Hyaline cartilage covering the epiphyses that reduces friction and absorbs shock at joints.

Diaphysis Function:

Provides leverage and weight support.

Epiphyses Function:

Allows for joint movement and contains red bone marrow for blood cell production.

Epiphyseal Plate Function:

Facilitates bone growth in childhood.

Medullary Cavity Function:

Stores fat and provides space for marrow.

Endosteum & Periosteum Function:

Assist in bone growth, repair, and nutrition.

Steps in Healing Fractures

1. Hematoma Formation,

2. Fibrocartilaginous Callus Formation,

3. Bony Callus Formation,

4. Bone Remodeling

Hematoma Formation:

Immediately after the fracture, blood vessels are ruptured, leading to a clot (hematoma) forming at the fracture site

Fibrocartilaginous Callus Formation:

Fibroblasts and chondroblasts produce a fibrocartilaginous callus (soft callus) to bridge the gap.

Bony Callus Formation:

Osteoblasts convert the fibrocartilaginous callus into a hard, bony callus.

Bone Remodeling:

The bony callus is remodeled by osteoclasts and osteoblasts to restore the bone to its original shape.

Surface Markings of Bones

Condyles, Facets, Head, Alveolus, Fossa, Sinus, Tubercle, Tuberosity

Condyles:

Rounded projections at the end of bones; articulate with other bones

Facets:

Smooth, flat areas that form joints with adjacent bones

Head:

Rounded, often enlarged end of a bone that fits into a joint

Alveolus:

Socket for a tooth in the jaw

Foramen:

Holes in bones for the passage of blood vessels, nerves, or ligaments

Fossa:

Shallow depression or cavity in a bone

Sinus:

Air-filled cavities in bones, reducing weight and resonating sound

Tubercle:

Small rounded bump or projection.

Tuberosity:

Large, roughened projection; muscle attachment site

Bones of the Skull

Frontal, Parietal, Occipital, Temporal, Sphenoid, Ethmoid

Frontal:

Forehead region, houses the frontal sinus.

Parietal

The skull has two that form the sides and roof of the cranium.

Occipital:

One; Back of the head; contains foramen magnum

Temporal

The skull has two that form side of the head; houses the ear and mastoid process.

Sphenoid:

One bat-shaped bone at the base; key to skull structure, highly vulnerable to fractures.

Ethmoid:

The skull has one that forms part of the nasal cavity and orbit

How many bones in the skull?

8

How many bones in the face?

14

Bones of the Face (Facial Bones)

Nasal, Maxillae, Zygomatic, Palatine, Lacrimal, Inferior nasal conchae, Vomer, Mandible

Nasal

The face has two that form the bridge of the nose.

Maxillae

The face has two that form the upper jaw, part of the orbit, and nasal cavity

Zygomatic

The two cheekbones, part of the orbit

Palatine

Two bones that are part of the hard palate and nasal cavity

Lacrimal

The two small bones in the inner eye orbit

What is the smallest bone in the body?

The Lacrimal

Inferior nasal conchae

Two bones that form the nasal cavity structures

Vomer

One bone that forms part of the nasal septum

Mandible

One bone that forms the lower jaw, the only movable skull bone.

Auditory Ossicles (bones)

Malleus, Incus, Stapes

Auditory Ossicles Functions

Transmit sound vibrations from the outer ear to the inner ear, allowing for hearing

Malleus aka

hammer

Incus aka

anvil

Stapes aka

stirrup

General Structure of Vertebral Column Structure

Composed of vertebrae, intervertebral discs, and ligaments

Functions of the Vertebral Column Structure

Supports the body, protects the spinal cord, absorbs shock, and allows for flexibility

Bones of the Vertebral Column

Cervical, Thoracic, Lumbar, Sacrum, Coccyx

How many Cervical Vertebrae?

7

Cervical

Located in the neck

C1

Atlas, controls yes motion, supports head

C2

axis, no motion

How many thoracic vertebrae

12