Comprehensive Study Notes: Human Anatomy and Physiology Question Collection on Anatomy and Physiology

INTRODUCTION TO ANATOMY AND ANATOMICAL PLANES

Human anatomy utilizes specific planes and terminology to describe positioning and sections. The body is divided by three primary planes: the median (sagittal) plane, which divides the body into left and right halves (antimeres); the frontal (coronal) plane, which is parallel to the forehead; and the horizontal (transverse) plane. Basic orientation terms describe relationships within these planes: superior and inferior (above and below), cranial and caudal (toward the head or tail), lateral and medial (away from or toward the midline), and anterior and posterior or ventral and dorsal (front and back). The human trunk is composed of the dorsum (back), abdomen, pelvis, and thorax.

ANATOMICAL NOMENCLATURE AND TERMINOLOGY

Medical Latin provides descriptive names for anatomical features. Structural extensions and junctions include the ramus (branch), arcus (arch), anulus (ring), angulus (angle), and processus (process or projection). Surface features are categorized as elevations or depressions: a tuber is a large bump, a tuberculum is a small tubercle, a tuberositas denotes a roughness, a crista is a ridge or crest, and a spina is a spine-like projection. Depressions include the fossa (trench or hollow), fovea (small pit), sulcus (groove), and incisura (notch). Openings or voids are termed foramen (hole), cavum (cavity), and squama (scale or plate). For the limbs, the upper extremity consists of the brachium (arm) and antebrachium (forearm) while the lower extremity features the femur (thigh) and crus (lower leg). Digit terminology refers to the pollex (thumb), hallux (big toe), index (pointing finger), digitus medius (middle finger), digitus anularis (fourth finger), and digitus minimus (pinky).

THE SKELETAL SYSTEM: AXIAL AND APPENDICULAR SKELETON

The adult human skeleton typically consists of $206$ bones. It is divided into the axial skeleton, comprising the cranium (skull), columna vertebralis (spine), and thorax (ribcage and sternum), and the appendicular skeleton, which includes the limbs and the shoulder and pelvic girdles. The largest bone in the body is the femur, while the smallest is the stapes located in the middle ear. Bones are classified by shape: long bones (humerus, femur), short bones (carpal bones like the os pisiforme), flat bones (scapula, sternum, parietal bone), and irregular bones (vertebrae, pelvic bones). Pneumatic bones contain air-filled spaces (maxilla, frontal bone, sphenoid bone, ethmoid bone).

BONE ANATOMY AND HISTOLOGY

Long bones are structured with a central diaphysis (shaft) and two ends called epiphyses. The junction between them is the metaphysis, which serves as the cartilaginous growth zone for longitudinal lengthening. The exterior surface of the bone is covered by a connective tissue membrane called the periosteum, while internal cavities, such as the medullary cavity (cavum medullare) containing bone marrow, are lined by the endosteum. Compact bone is composed of functional units called osteons. Specialized bone cells include osteoblasts, which form new bone tissue, and osteoclasts, which utilize lysosomal enzymes to resorb or break down bone.

THE CRANIUM: NEUROCRANIUM AND VISCEROCRANIUM

The skull (cranium) consists of $22$ bones (excluding ear ossicles). The neurocranium, which houses the brain, consists of $8$ bones: paried parietal and temporal bones, and unpaired frontal, ethmoid, sphenoid, and occipital bones. The viscerocranium (facial skeleton) consists of $14$ bones, including the maxilla, mandible (the only mobile bone), zygomatic (cheek), nasal, lacrimal, palatine, vomer, and inferior nasal concha. The sphenoid bone occupies the central part of the skull base, containing the sella turcica where the pituitary gland sits. The ethmoid bone contains the lamina cribrosa (perforated plate) for the first cranial nerve. Major openings in the skull base facilitate nerve and vessel passage: the foramen magnum (spinal cord passway in the occipital bone), foramen ovale (mandibular nerve), foramen rotundum (maxillary nerve), and canalis opticus (optic nerve).

THE VERTEBRAL COLUMN (COLUMNA VERTEBRALIS)

The spinal column is approximately $70\,cm$ long in adults and contains cervical ($7$), thoracic ($12$), lumbar ($5$), sacral ($5$ fused), and coccygeal ($3$ to $5$ fused) vertebrae. It exhibits physiological curvatures in the sagittal plane: cervical and lumbar lordoses (convex forward) and thoracic and sacral kyphoses (convex backward). A typical vertebra consists of a corpus (body) and an arcus (arch), which together form the vertebral foramen. Successive foramen create the vertebral canal (canalis vertebralis) for the spinal cord. Spinal nerves exit through the intervertebral foramina. Distinct vertebrae include the C1 (atlas), which lacks a body, and the C2 (axis), which features the dens (odontoid process).

THE THORACIC SKELETON: RIBS AND STERNUM

The thorax includes $12$ pairs of ribs (costae). Ribs $1$ through $7$ are "true" ribs (costae verae) directly attached to the sternum. Ribs $8$ through $10$ are "false" ribs (costae spuriae) attached to the cartilage of the rib above, and ribs $11$ through $12$ are "floating" ribs (costae fluctuantes). The sternum (breastbone) consists of the manubrium (superior part), corpus sterni (body), and the xiphoid process (processus xyphoideus).

THE APPENDICULAR SKELETON: UPPER AND LOWER LIMBS

The upper limb's shoulder girdle consists of the clavicle and scapula. The scapula features the acromion, coracoid process, and the glenoid cavity for articulation with the humerus. The forearm contains the radius (lateral) and the ulna (medial), with the olecranon forming the point of the elbow. The hand includes $8$ carpal bones, $5$ metacarpals, and $14$ phalanges. The lower limb's pelvic girdle is formed by the two hip bones (os coxae), each made of the fused ilium, ischium, and pubis. The acetabulum is the deep socket for the femur. The lower leg contains the tibia (medial/weight-bearing) and the fibula (lateral), with the patella being the largest sesamoid bone. The foot consists of the tarsus ($7$ bones), metatarsus ($5$ bones), and phalanges ($14$ bones).

ARTHROLOGY: THE JOINT SYSTEM

Joints are classified by mobility into synarthroses (immobile) and diarthroses (synovial/mobile). Synarthroses include syndesmoses (fibrous), synchondroses (cartilaginous), and synostoses (bony fusion like the sacrum). Synovial joints (articulationes synoviales) possess basic components: facies articularis (articular surfaces), capsula articularis (joint capsule), and cavitas articularis (joint cavity) containing synovia (joint fluid). Auxiliary parts include ligaments, disci and menisci (to increase congruency), bursae, and fat pads. Joint shapes determine movement: sphereoid (ball-and-socket, e.g., shoulder), ginglymus (hinge, e.g., fingers), trochoid (pivot), and plana (gliding).

THE MUSCULAR SYSTEM

Muscles are categorized into groups such as facial (mimic) muscles, masticatory (chewing) muscles, and muscles of the neck, chest, back, and limbs. Mimic muscles, such as the orbicularis oculi and orbicularis oris, are innervated by the VII cranial nerve. Masticatory muscles include the masseter, temporalis, and pterygoids. The diaphragm (ošit) is the primary respiratory muscle, featuring openings for the aorta (at $Th12$), esophagus (at $Th10$), and inferior vena cava (at $Th8-9$). Limb muscles are grouped into compartments: the upper arm has the biceps (flexor) and triceps (extensor), while the leg features the quadriceps femoris (thigh extensor) and the triceps surae (calf muscle attaching via the Achilles tendon to the calcaneus).

THE DIGESTIVE SYSTEM (APPARATUS DIGESTORIUS)

The digestive system includes the oral cavity, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (caecum, colon segments, rectum), and associated glands (liver, pancreas, salivary glands). The stomach features a cardia (inlet), fundus, corpus, and pylorus (outlet at $Th11$ level). The liver is the body's largest gland, receiving nutrient-rich blood via the portal vein. The pancreas functions as both an exocrine and endocrine gland, producing digestive enzymes and hormones like insulin and glucagon.

THE RESPIRATORY SYSTEM (APPARATUS RESPIRATORIUS)

The respiratory system is divided into upper tracts (nasal cavity, pharynx) and lower tracts (larynx, trachea, bronchi, lungs). The larynx contains the vocal folds and is supported by nine cartilages, including the thyroid, cricoid, and epiglottis. The trachea bifurcates into the left and right main bronchi at the carina ($Th4$ level). The lungs are divided into lobes ($3$ on the right, $2$ on the left) and are wrapped in the pleura (visceral and parietal layers). Gas exchange occurs in the alveoli.

THE URINARY SYSTEM (APPARATUS URINARIUS)

The urinary system consists of the kidneys (ren), ureters, urinary bladder (vesica urinaria), and urethra. The kidneys are retroperitoneal organs ($Th12-L3$ level) whose functional unit is the nephron. A nephron consists of a renal corpuscle (Malpighi's body) and a system of tubules (proximal, Henle's loop, distal). Humans produce approximately $1.5\,l$ of urine daily from $180\,l$ of primary filtrate. The bladder is a hollow muscular organ located behind the pubic symphysis, featuring a smooth triangular region called the trigonum vesicae.

THE REPRODUCTIVE SYSTEM (APPARATUS GENITALIS)

The male system includes the testes (producing sperm and testosterone), epididymis, ductus deferens, prostate, seminal vesicles, and penis. The female system includes the ovaries (producing eggs and hormones), uterine tubes, uterus (womb), and vagina. The uterus is characterized by three layers: perimetrium, myometrium (muscle), and endometrium (inner lining that sheds during menstruation). It is usually positioned in anteversion and anteflexion.

THE ENDOCRINE SYSTEM

Endocrine glands secrete hormones directly into the bloodstream. The pituitary gland (hypophysis), sitting in the sella turcica, is the "master gland" controlled by the hypothalamus. It consists of the adenohypophysis (anterior lobe) and neurohypophysis (posterior lobe). Other major glands include the epiphysis (melatonin), thyroid gland (T3, T4, and calcitronin), parathyroid glands (PTH for calcium balance), adrenal glands (cortex for steroids, medulla for adrenaline), and the pancreatic islets of Langerhans.

THE CENTRAL AND PERIPHERAL NERVOUS SYSTEM

The nervous system is divided into the Central Nervous System (CNS - brain and spinal cord) and the Peripheral Nervous System (PNS - cranial and spinal nerves). The brain (encephalon) includes the cerebrum, diencephalon (thalamus, hypothalamus), brainstem (mesencephalon, pons, medulla oblongata), and cerebellum (responsible for balance). The brain is protected by three meninges: the dura mater, arachnoid mater, and pia mater. There are $12$ pairs of cranial nerves and $31$ pairs of spinal nerves. The autonomic nervous system includes the sympathetic (stress response) and parasympathetic (rest and digest) divisions.

SENSORY ORGANS (ORGANA SENSUUM)

The senses include vision (eye), hearing and balance (ear), smell (nasal receptors), taste (tongue papillae), and touch (skin). The eye (bulbus oculi) has three layers: outer fibrous (sclera/cornea), middle vascular (choroid, ciliary body, iris), and inner neural (retina). The ear includes the external ear, middle ear (containing the malleus, incus, and stapes), and internal ear (cochlea for hearing and vestibule/semicircular canals for balance). The skin (dermis and epidermis) serves as a protective barrier and thermoregulator.