Unit 1 – Introduction to Anatomy and Physiology

Normal Anatomical Position and Significance

The standard anatomical position provides a universal reference for describing body structures:

• Body standing upright
• Feet parallel and flat on the floor
• Arms at the sides
• Palms facing forward with thumbs pointing away from the body

This consistent reference point prevents confusion when locating structures or describing injuries. When the body is in any other position, directional terms still refer to this standard position.

Body Planes and Directional Terminology

Body planes are imaginary flat surfaces that slice through the body:

• Sagittal plane - divides the body into left and right portions
• Midsagittal plane - exactly midline, creating equal left and right halves
• Frontal (coronal) plane - divides the body into anterior (front) and posterior (back) sections
• Transverse (horizontal) plane - divides the body into superior (upper) and inferior (lower) parts

Directional Terms

These terms describe the location of body structures relative to each other:

Term	Definition	Example
Anterior/Ventral	Toward the front of the body	The sternum is anterior to the spine
Posterior/Dorsal	Toward the back of the body	The spine is posterior to the sternum
Superior	Above or closer to the head	The head is superior to the neck
Inferior	Below or closer to the feet	The feet are inferior to the knees
Medial	Toward the midline of the body	The nose is medial to the eyes
Lateral	Away from the midline of the body	The ears are lateral to the nose
Proximal	Closer to the point of attachment	The elbow is proximal to the wrist
Distal	Farther from the point of attachment	The fingers are distal to the wrist

Body Cavities

The body contains several major cavities that protect organs and allow them to expand and contract:

• Dorsal cavity - includes the cranial cavity (brain) and vertebral canal (spinal cord)
• Ventral cavity - divided into:
  • Thoracic cavity (pleural cavities, mediastinum, pericardial cavity)
  • Abdominopelvic cavity (abdominal and pelvic cavities)

The diaphragm separates the thoracic and abdominal cavities.

Abdominopelvic Quadrants and Regions

Clinicians divide the abdomen for diagnostic purposes:

• Four Quadrants - created by vertical and horizontal lines through the umbilicus:
  • Right Upper Quadrant (RUQ) - liver, gallbladder
  • Left Upper Quadrant (LUQ) - stomach, spleen
  • Right Lower Quadrant (RLQ) - appendix, right ovary
  • Left Lower Quadrant (LLQ) - left ovary, sigmoid colon
• Nine Regions - more detailed division using two horizontal and two vertical lines:
  • Right hypochondriac, Epigastric, Left hypochondriac
  • Right lumbar, Umbilical, Left lumbar
  • Right iliac, Hypogastric, Left iliac

Unit 2 – Homeostatic Mechanisms and Clinical Significance

Homeostasis is a dynamic process involving continuous monitoring and adjustment of physiological variables. For example, body temperature remains around 37°C through mechanisms like sweating or shivering.

Components of Feedback Systems

Homeostatic control operates through feedback loops with three components:

1. Sensor (Receptor) - detects changes in physiological values (e.g., thermoreceptors detecting cold)
2. Control Center - compares sensor input to set point and sends instructions (often the brain or endocrine gland)
3. Effector - produces a response that returns the value toward the set point (e.g., muscles shivering to generate heat)

Types of Feedback Loops

Type	Mechanism	Examples
Negative Feedback	Reverses deviations from set point; promotes stability	Body temperature regulation, Blood glucose control, Blood pressure regulation
Positive Feedback	Amplifies initial change until endpoint is reached	Childbirth (oxytocin release), Blood clotting, Action potential generation

Unit 3 – Musculoskeletal System

Divisions of the Skeleton

Division	Components	Function	Number of Bones
Axial Skeleton	Skull, vertebral column, thoracic cage, hyoid bone, ear ossicles	Supports and protects brain, spinal cord, heart, and lungs; provides attachment sites for muscles	80 bones
Appendicular Skeleton	Upper and lower limbs, pectoral and pelvic girdles	Facilitates movement; lower limbs adapted for weight-bearing, upper limbs for mobility and dexterity	126 bones

Classification of Joints

Joints are classified both structurally and functionally:

Structural Classification

• Fibrous joints - bones joined by dense connective tissue; mostly immovable (e.g., skull sutures)
• Cartilaginous joints - bones connected by cartilage; allow limited movement (e.g., pubic symphysis, intervertebral discs)
• Synovial joints - contain a fluid-filled synovial cavity; permit free movement (e.g., shoulder, knee, hip)

Functional Classification

• Synarthrosis - immovable joints (e.g., skull sutures)
• Amphiarthrosis - slightly movable joints (e.g., intervertebral discs)
• Diarthrosis - freely movable joints; all synovial joints fall into this category

Muscle Types and Characteristics

Muscle Type	Structure	Control	Function	Location
Skeletal Muscle	Long, cylindrical, multinucleated, striated	Voluntary	Movement, posture, heat production	Attached to bones
Cardiac Muscle	Branched, striated, single nucleus, intercalated discs	Involuntary	Pumps blood through circulatory system	Heart
Smooth Muscle	Spindle-shaped, non-striated, single nucleus	Involuntary	Moves substances through internal passageways	Walls of hollow organs, blood vessels

Unit 4 – Integumentary System

Skin Layers and Functions

The skin has two main layers:

• Epidermis - outer layer of keratinized stratified squamous epithelium
• Dermis - inner layer of dense irregular connective tissue containing blood vessels, nerves, and accessory structures

Deep to the dermis is the hypodermis (subcutaneous layer) consisting of loose connective and adipose tissue.

Epidermal Layers (from deep to superficial):

1. Stratum basale - deepest layer with active cell division
2. Stratum spinosum - several layers of keratinocytes
3. Stratum granulosum - cells accumulate keratin and begin to degenerate
4. Stratum lucidum - clear layer found only in thick skin (palms, soles)
5. Stratum corneum - outermost layer of dead, keratinized cells that are continuously shed

Accessory Structures

• Hair - keratinous filament originating from hair follicles; provides protection, sensory input, and thermoregulation
• Nails - plates of densely packed dead keratinocytes; protect distal phalanges and assist with manipulation
• Sweat glands -
  • Eccrine glands - produce watery sweat for thermoregulation
  • Apocrine glands - secrete thicker fluid rich in organic molecules; associated with hair follicles
• Sebaceous glands - produce sebum (oil) to lubricate skin and hair

Effects of Aging on the Integumentary System

• Epidermis thins and stem cell division slows, making skin more prone to injury
• Collagen in dermis decreases, leading to wrinkles and loss of elasticity
• Reduced glandular activity results in dry skin
• Melanocyte activity declines, causing hair to turn gray
• Wound healing slows due to decreased blood supply and cell proliferation

Unit 5 – Role of Blood in Human Physiology

Functions of Blood

Blood is a specialized connective tissue with multiple vital functions:

• Transportation - delivers oxygen, nutrients, hormones; removes wastes like carbon dioxide and urea
• Defense - leukocytes protect from pathogens; platelets and plasma proteins form clots
• Homeostasis - distributes heat, regulates pH through buffers, maintains fluid balance

Composition of Blood

Component	Percentage	Composition	Function
Plasma	55%	Water (92%), proteins (7%), other solutes (1%)	Transport medium, clotting, immunity, pH balance
Formed Elements	45%	Erythrocytes, leukocytes, platelets	Gas transport, immunity, clotting

Major Plasma Proteins:

• Albumin - maintains osmotic pressure, transports substances
• Globulins - include antibodies (immunoglobulins) and transport proteins
• Fibrinogen - essential for blood clotting

Structure and Function of Cellular Components

• Erythrocytes (RBCs) - biconcave discs lacking nuclei; contain hemoglobin for oxygen transport
• Leukocytes (WBCs) - defend against pathogens; types include neutrophils, lymphocytes, monocytes, eosinophils, basophils
• Platelets - cell fragments derived from megakaryocytes; essential for hemostasis

Significance of Blood Groups

Blood groups are determined by antigens on erythrocyte membranes:

ABO Blood Group System:

• Type A - has A antigens and anti-B antibodies
• Type B - has B antigens and anti-A antibodies
• Type AB - has both A and B antigens, no antibodies (universal recipient)
• Type O - has no A or B antigens, both anti-A and anti-B antibodies (universal donor)

Rh Blood Group System:

• Presence of Rh (D) antigen denotes Rh positivity
• Absence denotes Rh negativity
• Rh incompatibility between an Rh− mother and Rh+ fetus can cause hemolytic disease of the newborn