C H A P T E R O N E

Introduction to the Human Body

Understanding the Human Body

Curiosity Illnesses, injuries, death

Obtained knowledge regarding the human body as science and medicine advanced

Anatomy: examines the structures, or morphology, or body parts – their forms, organization -tomy: (Greek) cutting up Anatomists rely on examination

Physiology: considers the functions of body parts – what they do and how they do it Also Greek origin; relationship to

nature Physiologists rely on experimentation

A few definitions…

Regional anatomy: study of anatomy based on regions or divisions of the body; emphasis on relations between the structures of that region

Systemic anatomy: study of anatomy based on body systems and their functioning throughout the body

Gross anatomy: study of anatomy that is visible to the naked eye; macroscopic

Microscopic anatomy: study of anatomy at the microscopic level; cells

Levels of OrganizationThe human body is composed of parts within parts, which

vary in complexity

Maintenance of Life

Requirements of Organisms Water metabolic processes; transport of

substances Food/Nutrients energy Oxygen release energy from food substances Heat regulation of metabolic reaction rates Pressure breathing (atmospheric); blood

circulation (hydrostatic)Although we require the aforementioned,

these factors alone are not enough to ensure survival; quality and quantity matter.

HomeostasisEquilibrium of the body’s internal environment

produced by the interaction of organ systems and regulatory processes (feedback systems). Homeostasis is a dynamic condition in response to

changing conditions. So important that it requires most of our metabolic energy

CONTINUED…

Body maintains homeostasis through a number of self-regulating control systems – homoeostatic mechanisms Receptors: provide information

about the stimuli in the internal environment

Control center: includes a set point, tells what a particular value should be (body temperature)

Effectors: elicit responses that alter conditions in the internal environment ; muscles or glands

Feedback Mechanisms

Negative feedback: almost all homeostatic control mechanisms are negative feedback mechanisms. These mechanisms reduce the variable back to its original state or “ideal value”. Blood sugar receptors sense the change pancreas

(control center) secretes insulin blood sugar levels reduce

Positive feedback:  the output enhances the original stimulus. Child birth: oxytocin is released that intensifies and

speeds up contractions. Blood clotting: vessel is damaged, platelets start to

cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed.

Just remember that positive feedback mechanisms

enhance the original stimulus and negative feedback mechanisms inhibit it.

D AY T W O – C H A P T E R O N E

Body Cavities and Terminology

Anatomical Position

Standing straight, body erect

Feet slightly apart Palms facing forward Thumbs point away

from body

Body PlanesSagittal: divides the

body into right and left parts

Frontal/coronal: divides the body into anterior and posterior parts

Transverse: divides the body into superior and inferior parts

Superior

Inferior

Body CavitiesDorsal cavity: protects the nervous

system, and is divided into two subdivisionsCranial cavity: within the skull; encases the

brainVertebral cavity: runs within the vertebral

column; encases the spinal cordVentral cavity: houses the internal

organs (viscera), and is divided into two subdivisions

ThoracicAbdominopelvic

Any fluid filled space in a multicellular organism

Cranial cavity

(contains brain)

Diaphragm

Abdominal cavity(contains digestive

viscera)

Pelvic cavity(contains bladder,

reproductive organs,and rectum)

Vertebral cavity(contains spinal

cord)

Key:

Dorsal body cavity

Ventral body cavity

Thoracic cavity

(contains heartand lungs)

(a) Lateral view

Dorsalbody

cavity

Ventral body cavity

(thoracic and abdominopelvic

cavities)

Thoracic cavity is subdivided into two pleural cavities, the mediastinum, and the pericardial cavity Right & Left Pleural

cavities: each houses a lung Mediastinum: contains the

pericardial cavity; surrounds the remaining thoracic organs Pericardial cavity: encloses

the heart

Thoracic Cavity

Figure 1.9b(b) Anterior view

Superiormediastinum

Pleuralcavity

Cranialcavity

Vertebralcavity

Pericardialcavity

Thoraciccavity(contains

heartand lungs)

Key:

Dorsal body cavity

Ventral body cavity

Abdominopelvic cavity

The abdominopelvic cavity is separated from the superior thoracic cavity by the dome-shaped diaphragm

Composed of two subdivisions Abdominal cavity–

contains the stomach, intestines, spleen, liver, gall bladder

Pelvic cavity– lies within the pelvis and contains the bladder, reproductive organs, and rectum

Body Cavities

Figure 1.9b

Abdomino-pelviccavity

Diaphragm

Abdominal cavity(contains digestive

viscera)

Pelvic cavity(contains bladder,

reproductive organs,and rectum)

Key:

Dorsal body cavity

Ventral body cavity

Facial/Head CavitiesOral and digestive – mouth and cavities of the digestive

organsNasal –located within and posterior to the noseOrbital – house the eyesMiddle ear – contains bones (ossicles) that transmit

sound vibrationsSynovial – joint cavities

ABDOMINOPELVIC REGIONS

Right upper

Left upperRight lower

Left lower

Figure 1.12

Abdominopelvic Quadrants