Intro to Human Anatomy and Physiology Flashcards
Introduction to Human Anatomy and Specialized Studies
The internal and structural components of the human body are organized into specialized systems that are studied through specific disciplines:
Osteology: The scientific study of bones, which form the structural framework of the body.
Arthrology: The study of joints, the sites where bones are articulated together.
Myology: The study of muscles, which generate movement by pulling on different body parts.
Neurovascular Anatomy: The study of the nerves and blood vessels throughout the body.
The human structural framework is composed of multiple materials: bones, cartilages, joints, ligaments, muscles, tendons, organs, glands, and the plates of the nose.
Skeleton Classification and Bone Morphology
The human skeleton is divided into two primary groups based on the long axis of the body:
Axial Skeleton: Represents the central axis and supports stability and posture. It consists of the bones of the head (skull), the trunk (vertebral column, ribs, and sternum).
Appendicular Skeleton: Consists of the bones of the upper and lower limbs.
Bones are classified by size and shape to describe their mechanical functions:
Long Bones: Found in the upper and lower limbs (e.g., humerus, femur).
Short Bones: Small, primarily cubic bones found in the hands and feet, such as the carpals and tarsals.
Flat Bones: Broad, thin bones found in the head, scapula (shoulder blade), and sternum.
Irregular Bones: Uniquely shaped bones that do not fit other categories, such as the vertebrae and certain skull bones.
Sesamoid Bones: Bones that exist suspended within soft tissue (tendons). These are not directly joined to other bones. A primary example is the patella (kneecap), which is suspended in the patellar tendon at the knee joint.
Arthrology: Structural and Functional Joint Classifications
Joints serve the primary function of enabling movement. They are classified by their structural composition:
Fibrous Joints: Composed heavily of fibrous tissue. These prioritize stability over mobility and are often nearly immobile. Examples include the sutures between skull bones and the connections between the radius and ulna.
Cartilaginous Joints: Composed of cartilage between bones. They provide limited movement. Examples include the joints between the sternum and ribs, between vertebrae, and the pelvic bones.
Synovial Joints: The most common and most movable type of joint in the body. They are characterized by a synovial cavity—a small space between articulated bones filled with synovial fluid. This fluid acts as a lubricant to reduce friction during movement.
Specialized types of synovial joints include:
Hinge Joint: Provides an "open and shut" range of motion, such as the elbow and knee.
Ball and Socket Joint: Provides the greatest range of motion, allowing multiple types of movement. Examples include the shoulder and hip joints.
Gliding Joint: Allows for sliding movements.
Saddle Joint: Allows movement in two planes.
Connective Tissues: Ligaments and Tendons
Ligaments and Tendons are string-like structures composed of fibrous connective tissue, primarily collagen for structural stability and elastin for stretchability.
Ligament: A band of tissue that connects bone to bone, reinforcing joints.
Tendon: A structure that connects muscles to other structures, such as bones or other muscles.
Anatomical Position and Directional Terminology
The Anatomical Position is the standard reference point: a person facing forward, standing upright, with hands at the side and palms facing the front.
Relative directional terms are defined in pairs to describe positions:
Anterior (Ventral): Toward the front of the body (e.g., the sternum is anterior to the heart).
Posterior (Dorsal): Toward the back of the body (e.g., the heart is posterior to the sternum).
Superior (Cranial): Toward the head (e.g., the nose is superior to the lips).
Inferior (Caudal): Toward the feet (e.g., the chin is inferior to the nose).
Medial: Closer to the imaginary midline of the body (e.g., the sternum is medial to the shoulder).
Lateral: Away from the midline (e.g., the shoulder is lateral to the sternum).
Superficial: Closer to the skin (e.g., abdominal muscles are superficial to the intestines).
Deep: Further from the skin (e.g., the heart is deep to the ribs).
Proximal: Closer to the trunk (used for limbs; e.g., the elbow is proximal to the wrist).
Distal: Further from the trunk (used for limbs; e.g., the toes are distal to the knee).
Sectional Anatomy: Planes and Dissections
To view deep structures, physicians use "optical dissections" like X-rays, MRI, or CT scans using standardized planes:
Sagittal Plane: Divides the body into right and left parts. A Mid-sagittal plane divides it into equal halves, while a Para-sagittal plane creates unequal divisions.
Transverse Plane: Slices the body into superior (top) and inferior (bottom) parts.
Frontal (Coronal) Plane: Divides the body into anterior (front) and posterior (back) parts.
Developmental Concepts and Vertebrate Characteristics
Humans are vertebrates and segmental animals. All vertebrate embryos possess four characteristic features during development:
Dorsal Hollow Nerve Cord: Develops into the brain and spinal cord.
Notochord: A long axial support structure that eventually breaks into fragments and forms the nucleus pulposis of intervertebral discs.
Pharyngeal Arches and Pouches: Develop into bones and muscles of the head and neck.
Vertebrae: The spinal components that persist throughout life.
Somites: Segmental groups of embryonic cells that lie in pairs along the developing nerve cord. They develop into:
Bones (vertebrae, ribs, sternum, limbs).
Cartilages.
Skin (dermis).
Muscles of the body wall and limbs.
Tendons and ligaments.
Segmental Structures: Serially repeating structures along the longitudinal axis (e.g., ribs, vertebrae).
Non-Segmental Structures: Systems that do not derive from somites, such as the digestive and respiratory systems. Nerves and blood vessels are non-segmental, though they appear paired because they supply segmental structures.
The Vertebral Column and Regional Organization
The vertebral column, or spine, is the collective structure of vertebrae and is divided into regions:
Cervical: vertebrae forming the neck.
Thoracic: vertebrae attached to the ribs.
Lumbar: vertebrae covering the lower abdomen.
Sacral: fused vertebrae forming the sacrum.
Coccygeal: to fused vertebrae forming the coccyx.
Typical Vertebra Anatomy:
Vertebral Body: The large, solid mass oriented anteriorly.
Vertebral Arch: Highlights the posterior portion of the vertebra, connected to the body by pedicles.
Lamina: The smooth surface of the arch.
Vertebral Foramen: The central opening in an individual vertebra. When stacked, these form the vertebral canal for the spinal cord.
Spinous Process: The pointy, most dorsal process.
Transverse Processes: Bilateral processes on the sides.
Articular Facets: Surfaces for connection with adjacent vertebrae.
Regional Distinction:
Cervical: Feature a transverse foramen for the vertebral artery and a bifid spinous process.
Thoracic: Feature costal facets for rib attachment.
Lumbar: Large bodies for weight-bearing; no transverse foramen or costal facets.
Special Vertebrae:
C1 (Atlas): Lacks a vertebral body; consists of anterior and posterior arches.
C2 (Axis): Features the dens (odontoid process) which allows the head to turn sideways.
Vertebral Ligaments and Intervertebral Discs
Stability and flexibility are provided by connective tissue structures:
Intervertebral Discs: Acts as cartilaginous joints. Composed of an outer annulus fibrosis and an inner gelatinous nucleus pulposis (a remnant of the embryonic notochord).
Anterior Longitudinal Ligament: Connects the anterior surfaces of vertebral bodies.
Posterior Longitudinal Ligament: Located on the posterior surface of the vertebral bodies.
Ligamentum Flavum: Named for its yellow color; connects the laminae of adjacent vertebrae.
Supraspinous Ligament: Connects the tips of spinous processes.
Nuchal Ligament: A continuation of the supraspinous ligament in the cervical region, supporting the head.
Spinal Curvatures:
Primary Curvatures: Present at birth (Thoracic and Sacral).
Secondary Curvatures: Form later to support the weight of the head and an upright posture (Cervical and Lumbar).
Abnormal Curvatures:
Scoliosis: Abnormal lateral deflection of the column.
Kyphosis: Exaggerated thoracic curvature ("hunchback").
Lordosis: Exaggerated lumbar curvature, often temporary during pregnancy.
Back Musculature: Epaxial and Hypaxial Divisions
Muscles are organized into layers and categorized by their position relative to the transverse processes:
Epaxial Muscles: Located dorsal to the transverse process; innervated by the dorsal rami. These are the true back muscles.
Hypaxial Muscles: Located ventral to the transverse process; innervated by the ventral rami. Includes the limbs and anterior/lateral body wall.
Epaxial Muscle Layers:
Superficial: Splenius (located in the neck and upper thorax).
Intermediate: The Erector Spinae group (composed of Iliocostalis, Longissimus, and Spinalis). These extend the spine.
Deep: Semispinalis (spans - vertebrae) and Multifidus (spans - vertebrae).
Muscle Action Principles:
Origin: The fixed attachment (typically inferior/medial).
Insertion: The mobile attachment (typically superior/lateral).
Flexion: Bending a joint to reduce the angle.
Extension: Straightening a joint to increase the angle.
Bilateral Action: Both sides of the body contract together (e.g., trunk flexion/extension).
Unilateral Action: Only one side contracts, leading to lateral flexion or rotation.
Central and Peripheral Nervous Systems
The nervous system is the body's primary communication network:
Central Nervous System (CNS): Regulatory centers comprising the brain and spinal cord.
Peripheral Nervous System (PNS): Nerves (cranial or spinal) that communicate between the CNS and the rest of the body.
The Spinal Cord:
Ends at the level of - in a cone-shaped tip called the conus medullaris.
Below the spinal cord, a collection of nerve roots resembling a "ponytail" is called the cauda equina.
Meninges: Protective layers covering the CNS.
Dura Mater: Tough outermost layer.
Arachnoid Mater: Middle layer with web-like projections.
Pia Mater: Thin innermost layer adhering to the nervous tissue.
Subarachnoid Space: Located between the arachnoid and pia, containing cerebrospinal fluid (CSF) for cushioning and nutrient exchange.
Spinal Cord Anatomy:
White Matter: Outer layer containing myelinated neurons.
Gray Matter: Inner H-shaped layer containing cell bodies and non-myelinated neurons. Divided into Dorsal Horns (sensory) and Ventral Horns (motor).
Somatic and Autonomic Subdivisions
Somatic Nervous System: Controls voluntary functions and communicates with somite-derived structures (skin, skeletal muscle).
Somatic Motor: A single neuron reaches from the ventral horn to the skeletal muscle.
Somatic Sensory: Afferent impulses from receptors (like pain in the skin) go to the CNS through the dorsal root ganglion.
Dermatomes: Areas of skin supplied by single spinal nerves.
Autonomic (Visceral) Nervous System: Controls involuntary functions (smooth muscle, heart, glands).
Visceral Motor Pathways: Require two neurons: a pre-ganglionic neuron (CNS to ganglion) and a post-ganglionic neuron (ganglion to organ).
Sympathetic Division: "Fight or Flight" response. Pre-ganglionic neurons originate from - lateral horns. Ganglia are organized as the sympathetic trunk next to the vertebral column.
Parasympathetic Division: "Rest and Digest" response. Pre-ganglionic neurons originate from the brain or , , sacral segments. Ganglia are located near the target organs.
Thoracic Anatomy, Respiration, and the Heart
Thoracic Skeleton: Consists of the thoracic vertebrae, sternum (Manubrium, Body, Xiphoid process), and pairs of ribs.
True Ribs (-): Attach directly to the sternum via individual costal cartilages.
False Ribs (-): Attach via shared costal cartilages.
Floating Ribs (-): No anterior attachment.
Thoracic Body Wall Muscles:
External Intercostals: Fibers run like "hands in pockets"; elevate ribs for inhalation.
Internal/Innermost Intercostals: Depress ribs during forceful exhalation.
Transversus Thoracis: Located on the posterior sternum; depresses ribs during forceful exhalation.
The Diaphragm: The primary muscle of breathing, separating the thoracic and abdominal cavities. It is innervated by the phrenic nerve (, , ). During contraction, it flattens to increase lung volume (inhalation).
Coelom and Serous Membranes: Organs are housed in cavities lined by double-layered membranes (parietal/outer and visceral/inner):
Pleura: Surrounds the lungs. Space between layers is the pleural cavity.
Pericardium: Surrounds the heart. The innermost layer is the epicardium.
Peritoneum: Lines the abdominal cavity.
Cardiac Anatomy:
The heart has four chambers: Right Atrium, Right Ventricle, Left Atrium, and Left Ventricle.
Valves: Prevent backflow of blood. Atrioventricular (AV) valves (tricuspid on right, bicuspid/mitral on left) and Semilunar valves (pulmonary and aortic).
Great Vessels: Superior/Inferior Vena Cava (drain into right atrium), Pulmonary Trunk (from right ventricle to lungs), Pulmonary Veins (to left atrium), Aorta (from left ventricle to body).
Abdominal Anatomy and the Digestive System
Abdominal Wall: Composed of layers—External Oblique, Internal Oblique, and Transversus Abdominus. The Rectus Abdominus ("six-pack") is located anteriorly, enclosed by the rectus sheath.
Digestive System Components:
Gut Tube: Includes the esophagus, stomach (churning food), small intestine (duodenum, jejunum, ileum), and large intestine (cecum, colon, rectum).
Accessory Organs (Gut Derivatives):
Liver: Produces bile, filters toxins, and synthesizes proteins.
Gallbladder: Stores and concentrates bile.
Pancreas: Produces digestive enzymes (taken to the duodenum via the pancreatic duct) and insulin/glucagon.
Mesenteries: Double layers of peritoneum that hold organs in place and store fat.
Ventral Mesentry: Falciform ligament (liver to wall) and Lesser omentum (stomach to liver). Lesser curvature
Dorsal Mesentry: Greater omentum (large apron-like structure from the stomach greater curvature) and Mesentery proper (holds small intestine).
Retroperitoneal Organs: Organs that lie behind the peritoneum and lack a mesentery, such as the kidneys, pancreas, and portions of the duodenum/colon.
Aponeurosis: A flat sheet of connective tissue that connects muscles to the parts they control. In the abdominal wall, aponeuroses serve to provide structural support and an attachment point for the muscles, contributing to the integrity of the abdominal cavity. The aponeurosis of the external oblique muscle forms the inguinal ligament, which plays a role in supporting the lower abdominal region.
Foregut: The foregut is the first section of the digestive system that extends from the mouth to the duodenum (the first part of the small intestine). It includes the esophagus, stomach, and the proximal part of the small intestine. The organs of the foregut receive blood supply from the celiac trunk.
Midgut: The midgut extends from the duodenum (second part) to the proximal two-thirds of the transverse colon. It includes the majority of the small intestine (jejunum and ileum) and receives blood from the superior mesenteric artery.
Hindgut: The hindgut is the terminal section of the digestive system, starting from the distal one-third of the transverse colon to the rectum. It includes the descending colon, sigmoid colon, and rectum. The hindgut is supplied by the inferior mesenteric artery.