The Human Body: Anatomical Regions,

Directions, Body Cavities, and Homeostasis

Credit: Carlos J Bidot Author 2006Revised 2010

Overview of Anatomy and Physiology

• AnatomyAnatomy – the study of the structure of body parts and their relationships to one another– Gross or macroscopic– Microscopic– Developmental

• PhysiologyPhysiology – the study of the function of the body’s structural machinery

Gross Anatomy

• RegionalRegional – all structures in one part of the body (such as the abdomen or leg)

• SystemicSystemic – gross anatomy of the body studied by system

• SurfaceSurface – study of internal structures as they relate to the overlying skin

Microscopic Anatomy

• CytologyCytology – study of the cell

• HistologyHistology – study of tissues

Developmental Anatomy

• Traces structural changes throughout life

• EmbryologyEmbryology – study of developmental changes of the body before birth

Specialized Branches of Anatomy

• Pathological anatomyPathological anatomy – study of structural changes caused by disease

• Radiographic anatomyRadiographic anatomy – study of internal structures visualized by X ray

• Molecular biologyMolecular biology – study of anatomical structures at a sub-cellular level

Physiology

• Considers the operation of specific Considers the operation of specific organ systemsorgan systems– Renal – kidney function– Neurophysiology – workings of the nervous

system– Cardiovascular – operation of the heart and

blood vessels

• Focuses on the functions of the Focuses on the functions of the body, often at the cellular or body, often at the cellular or molecular levelmolecular level

Chemical levelAtoms combine to form molecules

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Cellular levelCells are made up of molecules

Tissue levelTissues consist of similar types of cells

5 Organ system levelOrgan systems consist of different organs that work together closely

Organ levelOrgans are made up of different types of tissues

6 Organismal levelThe human organism is made up of many organ systems

Atoms

Molecules

Smooth muscle cell

Smooth muscle tissue

Connective tissue

Smooth muscle tissue

Epithelial tissue

Blood vessel (organ)

Heart

Blood vessels

Cardiovascular system

Levels of Structural Organization

Figure 1.1

Levels of Structural Organization

(*VERY important*)• ChemicalChemical – atoms combined to form molecules

• CellularCellular – cells are made of molecules• TissueTissue – consists of similar types of cells• OrganOrgan – made up of different types of

tissues• Organ systemOrgan system – consists of different

organs that work closely together• OrganismOrganism – made up of the organ

systems

Homeostasis

External environment – keeps changingInternal environment - remains stable. How?

Body has “Homeostatic Mechanisms”

Imagine one day is very cold out, while the next day is very hot.

What effect does that have on your body temperature?

Homeostasis

• HomeostasisHomeostasis is the ability to maintain a relatively stable internal environment in an ever-changing outside world

• The internal environment of the body is in a dynamic state of equilibriuma dynamic state of equilibrium

• Chemical, thermal, and neural factors interact to maintain homeostasis

Feedback Loops

• The beginning of a reflex pathway is a disturbance in a controlled parameter called a stimulus

• The stimulus is detected by a sensor (receptor)– continuously monitoring the environment– when a change is detected, it sends out a

signal

• The signal travels from the receptor to the control (integrating) center

Feedback Loops• The control center evaluates the incoming

signal, compares it to the homeostatic setpoint, and decides on the appropriate response

• The control center sends out a signal to the effector

• The effector is a cell or tissue that carries out the appropriate response to bring the parameter back to within normal limits (setpoint)

Types of Feedback

• Negative feedback– Most common– The effector removes the cause of

imbalance– Ex. Body temperature, blood pH

• Positive feedback– The effector reinforces the stimulus

(does not stop it)– Ex. Blood clotting, labor

Anatomical Position

• Body erect • Feet slightly apart• Palms facing

forward • Thumbs point

away from body

Figure 1.7a

Directional Terms

• Superior and inferiorSuperior and inferior – toward and away from the head, respectively

• Anterior and posteriorAnterior and posterior – toward the front and back of the body

• Medial, lateral, and intermediateMedial, lateral, and intermediate – toward the midline, away from the midline, and between a more medial and lateral structure

Directional Terms

• Proximal and distalProximal and distal – closer to and farther from the origin of the body

• Superficial and deepSuperficial and deep – toward and away from the body surface

Directional Terms Table 1.1

Directional Terms Table 1.1

Regional Terms: Anterior View

• AxialAxial – head, neck, and trunk

• AppendiculAppendicularar – appendages or limbs

• Specific Specific regional regional terminologyterminology

Figure 1.7a

Regional Terms: Posterior View

Figure 1.7b

Activity!

• https://www.wisc-online.com/learn/natural-science/life-science/ap15305/anatomical-terminology-relative-position

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Anatomical Locations• Abdominal: abdominal region• Acromial: the point of the shoulder• Antebrachial: forearm• Antecubital: anterior surface of the

elbow• Axillary: armpit• Brachial: upper arm• Buccal: cheek of the face• Calcaneal: heel of the foot• Carpal: wrist• Cephalic: head

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Anatomical Locations• Cervical: neck• Deltoid: round part of the shoulder• Digital: fingers and toes• Dorsum: back • Femoral: thigh• Frontal: forehead• Gluteal: buttocks• Hallux: big toe• Inguinal: groin• Lumbar: lower back• Mammary: breast

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Anatomical Locations• Mental: chin• Nasal: Nose• Occipital: base of the skull• Olecranal: elbow• Oral: mouth• Orbital: bony eye socket• Otic: ear• Palmar: palm of hand• Patellar: Kneecap• Pedal: Foot

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Anatomical Locations• Pelvic: pelvis region• Perineal: area between anus and

external genitals• Plantar: sole of foot• Pollex: thumb• Popliteal: behind the knee• Pubic: genital region• Sacral: lower back between the hips• Scapular: shoulder blade• Tarsal: ankle• Thoracic: chest• Vertebral: spine

Body Planes• SagittalSagittal – divides the body into right

and left parts• Midsagittal or medialMidsagittal or medial – sagittal

plane that lies on the midline• Frontal or coronalFrontal or coronal – divides the

body into anterior and posterior parts• Transverse or horizontalTransverse or horizontal (cross

section) – divides the body into superior and inferior parts

• Oblique sectionOblique section – cuts made diagonally

Body Planes Figure 1.8

Anatomical Variability

• Humans vary slightly in both Humans vary slightly in both external and internal anatomyexternal and internal anatomy

• Over 90% of all anatomical structures match textbook descriptions, but:– Nerves or blood vessels may be

somewhat out of place– Small muscles may be missing

• Extreme anatomical variations Extreme anatomical variations are seldom seenare seldom seen

Body Cavities

Figure 1.9a

Body Cavities• Dorsal cavityDorsal cavity protects the nervous

system, and is divided into two subdivisions– Cranial cavity is within the skull and

encases the brain– Vertebral cavity runs within the vertebral

column and encases the spinal cord• Ventral cavityVentral cavity houses the internal organs

(viscera), and is divided into two subdivisions: - Thoracic and Abdominopelvic cavities

Body CavitiesFigure 1.9b

Body Cavities

• Thoracic cavityThoracic cavity is subdivided into pleural cavities, the mediastinum, and the pericardial cavity– Pleural cavities – each houses a lung– Mediastinum – contains the

pericardial cavity, and surrounds the remaining thoracic organs

– Pericardial cavity – encloses the heart

Body Cavities• The abdominopelvic cavity is

separated from the superior thoracic cavity by the dome-shaped diaphragm

• It is composed of two subdivisions– Abdominal cavity – contains the

stomach, intestines, spleen, liver, and other organs

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

Ventral Body Cavity Membranes

• Parietal serosaParietal serosa lines internal body walls

• Visceral serosaVisceral serosa covers the internal organs

• Serous fluid separates the serosae (A serous membrane, especially one that lines the pericardial, pleural, and peritoneal cavities, enclosing their contents)

Ventral Body Cavity Membranes

Figure 1.10a

Ventral Body Cavity Membranes

Figure 1.10b

Other Body Cavities

• Oral and digestiveOral and digestive – mouth and cavities of the digestive organs

• NasalNasal –located within and posterior to the nose

• OrbitalOrbital – house the eyes• Middle earMiddle ear – contain bones (ossicles)

that transmit sound vibrations• SynovialSynovial – joint cavities

Abdominopelvic Regions

• Umbilical• Epigastric• Hypogastric• Right and left

iliac or inguinal• Right and left

lumbar• Right and left

hypochondriacFigure 1.11a

Organs of the Abdominopelvic Regions

Figure 1.11b

Abdominopelvic Quadrants

• Right upper (RUQ)

• Left upper (LUQ)

• Right lower (RLQ)

• Left lower (LLQ)

Figure 1.12