Comprehensive Notes on Human Anatomy and Physiology

Introduction to Anatomy and Physiology

The study and mastery of both anatomy and physiology are essential requirements for every health professional. These sciences enable the accurate understanding and precise localization of injuries, the mechanisms of their effects, the determination of their severity, and the assessment of prognosis. Furthermore, they serve as the cornerstone for all technical healthcare procedures. While anatomy is applied to organs as study units smaller than systems but larger than cells, it remains the foundation for nursing and midwifery students within the basic sciences unit. Mastery of this field allows for sound medical diagnosis and ensures that nurses and midwives can provide safe and appropriate health interventions for every case.

Basic Definitions: Anatomy and Physiology

Anatomy (Anatomie) is the science concerned with studying the constituent organs of the human body in terms of four primary aspects: their number, their shape, their structure, and their positioning. Physiology (Physiologie) is a term of Greek origin composed of two parts: "Physis," meaning nature or origin, and "Logy," meaning science. Therefore, physiology is the science dedicated to studying the functions of body organs in their natural state and the relationships that link them together.

The Cell: Structure and Function

The cell is the smallest living structural unit that builds a living organism. It performs various vital functions, including respiration, nutrition, movement, reproduction, and sensation. Living organisms are classified into two types based on their cellular complexity: Microorganisms, where the organism consists of a single cell and its life manifestations depend on a group of enzymes and yeasts; and Higher Organisms, where the organism consists of an unlimited group of cells and its life manifestations depend on a set of organs performing vital functions.

The internal components of a cell include the plasma membrane, cytoplasm, nucleus, nucleolus, nuclear pore, mitochondria, Golgi apparatus, lysosome (digestive body), ribosomes, centriole, microtubules, vesicles, and vacuoles. The endoplasmic reticulum is divided into two types: smooth and rough.

Tissue Classification and Histology

A tissue is a group of cells that cooperate or integrate to perform a specific bodily task. These cells are usually similar in shape, size, and vital function and may be interconnected. The science that studies the microscopic structure of cells forming tissues is called Anapate (Histology). There are four primary types of tissues in the human body.

Connective Tissue is the most diverse and widely distributed tissue in the human body. Its cells are often non-adjacent, leaving spaces occupied by an interstitial substance or body fluids known as the "ground substance." Examples include bone tissue (composed of three cell types gathered by ossein), blood tissue (composed of three cell types gathered by plasma), and seminal fluid (a connective tissue composed of a group of cells gathered by seminal substance).

Epithelial Tissue consists of closely packed cells arranged in one or more layers. It is divided into Covering/Lining Epithelia and Glands. Covering epithelia are membranes that cover the body surface and line most of its cavities; they include simple surface epithelia (such as the skin epidermis) and stratified/compound epithelia (such as the dermis and its layers). Glands are secreting epithelial tissues, categorized into three types: Exocrine glands (ductal glands like salivary and mammary glands), Endocrine glands (ductless glands that secrete directly into the blood like the ovaries, pituitary, and adrenal glands), and Mixed glands (secreting through both methods, such as the pancreas and liver).

Muscular Tissue consists of muscle cells that unite to form muscle fibers, which in turn form the fleshy mass known as a muscle. There are three types of muscles: Smooth muscles (white, involuntary muscles controlled by the autonomic nervous system, such as the intestines, stomach, and uterus); Striated muscles (red or skeletal, voluntary muscles controlled by the brain, such as the thigh and humerus muscles); and Cardiac muscle (striated but involuntary and self-moving).

Nervous Tissue consists of dendritic-shaped nerve cells whose branches cover various parts of the body. It forms the nervous system, which is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS consists of nerve cell nuclei protected within the skull and the length of the vertebral column; it includes the Brain (composed of the Cerebrum, Cerebellum, and Brainstem/Medulla Oblongata) and the Spinal Cord. The PNS consists of the dendritic extensions of nerve cells, including cranial nerves, spinal nerves, and their peripheral endings. Tissues can also be classified by consistency into soft tissues and hard tissues.

Biological Organization and Internal Organs

The hierarchy of life begins at the cellular level and progresses as follows: cells unite to form tissues; a group of tissues (even if different in shape, color, size, and function) unite to form an Organ; a group of different organs unite to form an Organ System; a group of vital systems unite to form a Living Organism; and groups of living organisms coexist to form a Community.

Internal organs of the human body include the Brain, Lungs (Right and Left), Stomach, Spleen, Pancreas, Large Intestine (Colon), Small Intestine, Thyroid Gland, Heart, Liver, Gallbladder, Kidneys, Ureters, and Bladder.

The Anatomical Position and Reference Planes

All anatomical terms and concepts used to describe the location and relationship between organs are based on the "Anatomical Position." In this standard reference position: the human body is upright and standing tall; the head is raised, the face is directed forward with a neutral expression, the mouth is closed, and the eyes look directly into the eyes of the observer; the arms are extended downward along the torso; the palms are open and facing forward, with fingers spread so the thumb forms a $90^{\circ}$ angle with the index finger; the soles of the feet are flat on the ground and parallel, with the toes pointing forward.

Anatomists use three imaginary planes to divide the body: The Midline (White Line) is a vertical line that divides the body into two symmetrical right and left halves. The Coronal (Frontal) Plane is a vertical line that divides the body into two asymmetrical parts: anterior (front) and posterior (back). The Horizontal (Transverse) Plane is an imaginary horizontal line parallel to the ground that divides the body into two parts: superior (upper) and inferior (lower).

Anatomical Directional Terminology

Directions are described using several key concepts: Lateral (far from the midline or other organs) and Medial (close to the midline or other organs); Superior (situated above the transverse plane or other organs) and Inferior (situated below the transverse plane or other organs); and Superficial (close to the skin surface) and Deep (far from the skin surface).

Anatomical Map of the External Abdominal Wall

The abdomen is divided into nine regions for diagnostic and descriptive purposes: 1. Right Hypochondrium; 2. Epigastric Region; 3. Left Hypochondrium; 4. Right Lumbar (Flank); 5. Umbilical Region; 6. Left Lumbar (Flank); 7. Right Iliac Fossa; 8. Hypogastric Region; 9. Left Iliac Fossa.

The Respiratory System: Respiration and Mechanics

Respiration is a vital function through which food materials are oxidized and their chemical bonds are broken to obtain energy and increase protoplasm. Its functions include providing the body with oxygen ($O_2$), expelling carbon dioxide ($CO_2$), and maintaining body temperature. Respiration consists of two processes: Inhalation (an active process requiring effort from respiratory organs to bring air into the lungs) and Exhalation (a passive or spontaneous process requiring no effort to expel air, though it can be forced).

Gas exchange occurs between the alveoli and blood capillaries through diffusion. Inhalation involves the entry of air assisted by the diaphragm and ribcage muscles, while exhalation involves the exit of air. Standard lung capacities include: Total Lung Capacity ($6\,L$), Vital Capacity ($\approx 3\,L$), and Tidal Volume ($500\,mL$).

Anatomy of the Respiratory Organs

The system is divided into upper and lower regions. The nose (single, but divided) is a pyramidal structure with a bony base, cartilaginous head/wings, covered by skin and lined with a hairy, vascular mucous membrane; it warms, filters, and moistens air. The pharynx is a conical structure common to both the respiratory and digestive systems, connecting the nose and mouth to the larynx and esophagus. The larynx contains four vocal cords that vibrate during exhalation to produce sound; it opens at the glottis, which is closed during swallowing by the epiglottis. The trachea (windpipe) is a cylindrical tube $10-12\,cm$ long, supported by semi-circular cartilaginous rings anteriorly and smooth muscles/ligaments posteriorly; it terminates at the level of the fourth thoracic vertebra. The bronchi (two) branch from the trachea into the right lung (dividing into three) and the left lung (dividing into two).

The lungs consist of the Right Lung (3 lobes) and the Left Lung (2 lobes, leaving space for the heart). They are spongy, elastic, and covered by the pleura, which has two layers: an outer layer adhering to the inner ribcage and an inner layer adhering to the lung surface, with pleural fluid between them. There are over $300 \text{ million}$ alveoli, providing a total surface area of $70-100\,m^2$ for gas exchange. The Diaphragm is a single, deep red muscular sheet that contracts and moves downward to expand the ribcage, creating negative pressure to draw air in.

Common respiratory diseases include Laryngitis, Sinusitis, Pulmonary Tuberculosis, Pulmonary Embolism, Broncho-pneumonia, Asthma, Pneumonia, Pleurisy, Pneumothorax, Lung Tumors, and Bronchial Tumors.

The Circulatory System: Overview and Heart Anatomy

The circulatory system comprises the heart as a central organ connected to a network of blood vessels that ensure blood circulation from fetal life until death. It transports $O_2$ and nutrients from the heart to the body and carries $CO_2$ and waste from cells to excretory organs. The heart is a single, hollow, striated involuntary muscle, roughly the size of a fist and weighing between $250 \text{ to } 300\,g$. It beats at a rate of $60-100 \text{ beats/minute}$ and pumps approximately $5\,L \text{ of blood/minute}$ ($7200\,L/day$). It is located slightly to the left of the midline, with its base at the top-right-back and its apex at the bottom-left-front.

The heart has four chambers: the Right Atrium (receives deoxygenated blood from the Superior Vena Cava, Inferior Vena Cava, and Coronary Sinus); the Right Ventricle (the origin of the Pulmonary Artery, separated from the right atrium by the tricuspid valve); the Left Atrium (receives oxygenated blood from the four pulmonary veins); and the Left Ventricle (the origin of the Aorta, separated from the left atrium by the mitral/bicuspid valve). Significant valves include the Aortic valve and Pulmonary valve. The heart muscle is nourished by the Right and Left Coronary Arteries.

Blood Vessels and Blood Composition

Arteries carry blood away from the heart; they have thick, elastic walls. The largest is the Aorta (originating from the left ventricle, forming the aortic arch), and others include the Carotid arteries (supplying the brain and head) and the Pulmonary artery (carrying deoxygenated blood to the lungs). Veins return blood to the heart and contain valves to prevent backflow; these include the Venae Cavae, Pulmonary veins, and Coronary veins. Capillaries are very thin vessels where gas and nutrient exchange occurs, with a total estimated length of about $100,000\,km$.

Blood is a bright red, viscous liquid forming a connective tissue. An adult has $5 \text{ to } 6\,L$ of blood. It has four functions: Respiratory ($O_2/CO_2$ transport), Nutritive (nutrient transport), Excretory (waste removal), and Immune (defense and clotting). Blood composition includes: Plasma (60% of volume, providing liquid consistency); Red Blood Cells (RBCs/Erythrocytes), which are non-nucleated, biconcave, contain hemoglobin, are produced in bone marrow, destroyed in the spleen after nearly $60 \text{ days}$, and number $4.5-5 \text{ million/mL}$; White Blood Cells (WBCs/Leukocytes), which fight infection and number $6-9 \text{ thousand/mL}$; and Platelets (Thrombocytes), which are colorless, flat cells that form clots to stop bleeding, are produced in bone marrow, destroyed in the spleen, and number $200-700 \text{ thousand/mm}^3$.

White Blood Cells Classifications and Circulation

White blood cells (NFS differential count) include: Neutrophils ($60-75\%$), Eosinophils ($1-5\%$), Basophils ($1\%$), Lymphocytes ($25-30\%$), and Monocytes ($2-10\%$). Types of circulation include: Major (Systemic) Circulation, the path through the whole body except the lungs to deliver oxygen and nutrients; Minor (Pulmonary) Circulation, the path between the heart and lungs for gas exchange; and Specialized (Local) Circulation, such as blood flow specifically to the heart or liver.

Common cardiovascular conditions include Right Heart Failure, Left Heart Failure, Cardiac Arrest, Myocardial Infarction, Arterial Hypertension, Atherosclerosis, Leukemia, Coagulation Disorders, Septicemia, Vascular Accidents, and Endocarditis.

Introduction to the Digestive System

The digestive tract begins with the Mouth, an oval cavity located below the nose. It consists of the vestibule (between teeth and lips/cheeks) and the oral cavity proper (inside the teeth, reaching the pharynx). The Tongue is a single, red conical organ fixed by a ligament (frenulum) to the floor of the mouth; it serves as the receptor for taste, aids in speech, and moves food for swallowing. In adults, there are $32$ teeth: 16 in the upper jaw and 16 in the lower jaw, categorized as 8 incisors, 4 canines, and 20 molars (8 premolars and 12 molars). These white structures are made of dentin and covered in enamel for cutting, tearing, and grinding food.

The Salivary Glands consist of six glands (three pairs). The Parotid Glands are the largest, located in front of and below the ears, opening near the second upper molar to secrete serous fluid during eating. The Submandibular Glands are located below the lower jaw angle, opening next to the lingual frenulum. The Sublingual Glands are the smallest, located at the floor of the mouth under the tongue tip, secreting a mucous-serous fluid during speech.