Levels of Organization and Body Cavities

 

Levels of Organization and Body Cavities

The body is studied in seven structural levels:

Chemical: involves interaction among atoms and their combination into molecules

Organelle: small structure contained within a cell that performs one or more specific function

Cell: basic functional units of life, cells share many characteristics, but differ in structure and function

Tissue: group of cells with similar structures and functions

Organ: Composed of two or more tissue types that together perform one or more common function

Organ system: group of organs classifies as a unity because of a common function or set of function

Organism: any living thing considered as a whole, organisms can have anywhere from a single cell to trillions of cells

Body Cavities

Cavity: fluid- filled space in the body that holds and protects internal organs

Ventral cavity: (front of the body) contains three major cavities…

• Thoracic cavity: surrounded by rib cage and separated from the abdominal cavity by the diaphragm

• Abdominal cavity: bounded by the abdominal muscles below the thoracic cavity and contains the stomach intestines, liver, spleen, pancreas, and kidneys

• Pelvic cavity: enclosed by the bones of the pelvis and contains the urinary bladder, part of the intestines, and internal reproductive organs. The abdominal and pelvic cavities are sometimes referred to as the abdominopelvic cavity

Dorsal cavity: back of the human body, and it is subdivided into two cavities…

• Cranial cavity: contains the brain

• Spinal cavity: contains the spinal cord

Terminology

Anatomical position: person standing erect with the fette forward, arms hanging to the sides, and the palms of the hands facing forward

Term	Definition
Inferior	Structure below another
Superior	Structure above another
Anterior	Toward the front of the body
Posterior	Toward the back of the body
Dorsal	Toward the back
Ventral	Toward the front
Proximal	Closer to the point of attachment to the body than another structure
Distal	Farther from the point of attachment to the body
Lateral	Away from the midline of the body
Medial	Toward the middle or midline of the body
Superficial	Toward or in the surface
Deep	Away from the surface
Anterosuperior	In front or above the surface
Midline	Median line
Supine position	Lying flat with face and torso facing upward
Prone position	Lying face down

Anatomical view

1. Anterior view 

2. Posterior view 

Terminology Anterior view

Posterior view

Cephalic -head  Cranial -skull  Facial- face  cervical - neck  Axillary -armpit  Brachial- arm Antecubital- front of elbow  Antebrachial- front of forearm Carpal -wrist  Palmar-palm Pollex -thumb Digital or phalangeal - Finger  Femoral - Thigh Patella -Front of knee  Crural -shin  Pedal -Foot  Tarsal- Ankle  Digital or Phalangeal - Toes  Dorsum -Top of foot  Hallux -great toe Sternal-breastbone Thoracic- Chest Mammary- Breast  Abdominal-abdomen  Umbilical-navel  Coxa-hip Pelvic- Pelvis  Inguinal-Groin Pubic- Pubis  Dorsum-back of hand  Manual-Hand  Frontal-Forehead Temporal- Temple  Orbital or ocular- eye  Otic -ear Buccal- cheek  Nasal- Nose  Oral-Mouth  Mental-  Chin

Occipital -Base of the skull Acromial-shoulder Scapular-shoulder blade  Vertebral- Spinal Column Dorsal-Back  Olecranal back of elbow  Cubital back of elbow  Olecranal or cubital ( back of elbow) Lumbar- loin  Sacral -between hips  coccygeal -tailbone Gluteal-buttok Perineal-area between anus and external genitals  Popliteal- back of knee Sural-calf  plantar-Sole  Calcaneal- Heel

Body Planes 

Anatomical Planes divide the body into two (the plane applies to organs which can also be divided along planes.

Sagittal plane: runs vertically through the body and separates the body into right and left parts

Midsagittal plane: divides the body into two equal halves

Transverse plane: runs parallel to the surface of the ground and divides the body into superior and inferior planes

Frontal or Coronal plane: runs vertically from left to right and divides the body into anterior and posterior parts 

Coronal or Frontal Plane is a front and back division 

Transverse or cross sectional plane is a top and bottom division

Sagittal or median indicates a left and right division

Anatomical Direction : 

• superior and inferior 

• Anterior and posterior 

• Lateral and medial 

Two directional terms : 

• Anteroposterior 

• Posteroinferior 

Distal and proximal are used to indicate which structure is closer Proximal to the structure or farther away (distal ) 

• Lateral and medial are used to determine which structure is close to the medial line, which divides a body into right and left sides . 

• The rib cage is lateral to the sternum ( breast bone), where the sternum is medial to the ribcage. 

• Anatomical direction also includes right and left 

Body Regions:

Upper limb: includes arm, forearm, wrist, and hand

Lower limb: decided into the thigh, leg, ankle, and foot

Central region: includes the neck and trunk

Head region: includes the entire head

Human Tissues

Tissue: group of cells with similar structure and function and similar extracellular substances located between the cells

Tissue	Structure	Function	Example
Connective	Characterized by extracellular material that separate cells from one another	Enclosing and separating Connecting tissues to one another Supportive and moving Storing  Cushioning and insulating Transporting  Protecting	Cells of the immune system and blood
Epithelial	Classified according to the number of cell layers and shapes	Protecting underlying structures Acting as barriers Permitting the passage of substances Secreting substances	Skin, linings of internal organs
Muscle	Cells of muscles resemble long thread and are called fibers	Providing movement	Heart, organs of digestive system
Neural	Cells are composed of dendrites	Coordinating and controlling many body activities	Brain, spinal cord

 

Four Types of Tissue