6 level of body organization

1 - chemical

2 - cellular

3 - tissue

4 - organ

5 - organ system

6 - organism

11 organ systems

01 - integumentary system (hair, skin, nails)

02 - skeletal system

03 - muscular system

04 - cardiovascular system

05 - nervous system

06 - digestive system

07 - reproductive system

08 - endocrine system

09 - respiratory system

10 - urinary system

11 - lymphatic and immune system

integument - a natural covering, such as skin, hair, rind, or shell

Structural: integumentary, skeletal, muscular

Distributive: cardiovascular, lymphatic

Metabolic: digestive, urinary, respiratory

Control: nervous, endocrine

Procreative: reproductive

Methods of examination

palpation - examination by feeling body surfaces by hand (of the examiner)

auscultation - listening to body sounds (with a stethoscope)

percussion - tapping on a body surface to listen to specific echoes

Characteristics of the living human organism

The six most important life processes of the human body

1. metabolism

2. responsiveness (to internal, external environment)

3. movement (of the body, organs, cells, or organelles)

4. growth

5. differentiation (cells develop from unspecialized to specialized)

6. reproduction (either of new tissue to replace old one, or the production of new individuals)

homeostasis - relative balance of the internal environment of the body (a dynamic physiological constancy)

Body fluids

ICF = intracellular fluid

ECF = extracellular fluid (interstitial fluid)

ECF in blood = blood plasma

ECF in lymphatic vessels = lymph

ECF around brain and spinal cord = cerebrospinal fluid

ECF in joints = synovial fluid

ECF in the eyes = aqueous humor and vitreous body

Interstitial fluid surrounds all body cells and therefore is referred to as “internal environment” of the body.

Control of homeostasis

The nervous system and the endocrine system control homeostasis, either in concert or independently.

Glands release hormones into the blood.

Three basic components of a feedback system: receptor (receives nerve impulse or chemical signal), control center (output as nerve impulse, hormone, or other chemical signal), effector (produces a response; nearly every organ or tissue in the body can behave as effector)

Negative feedback cycle reverses original stimulus - returns the body to a previous homeostatic condition, interrupts the effect of a stimulus; moves a bodily function in the opposite direction as a change that has been detected by a receptor

Positive feedback cycle enhances original stimulus - moves a bodily function into the same direction as a change that has been reported by a receptor; for example, at the first signs of labor, more labor symptoms are effected

A positive feedback loop has to be stopped by an outside event (e.g. baby born); while negative feedback systems are constantly at work, positive feedback systems play a role in extraordinary events.

Imbalances

A disorder is a general lack of optimal function.

A disease is a rather specific disorder.

A sign is an indicator of a disorder or disease that can be observed by another person. E.G., vital signs: blood pressure, body temperature

A symptom is an indicator that is felt by the individual who is sick, such as nausea, feeling weak, etc.

Anatomical terminology

Anatomical position - standing and facing the observer, palms of the hands facing observer

Prone position - lying face down

Supine position - lying face up

Regional names: head, neck, trunk, upper limbs, lower limbs

Anatomical descriptive adjectives for body parts:

Cephalic (area, features, disorders) - related to the head

Cranial - related to the scull

Facial - related to the face

Frontal - related to the forehead

Orbital - related to the eye

Otic - related to the ear

Nasal - related to the nose

Buccal - related to the cheeks

Oral - related to the mouth

Mental - related to the chin

Occipital - related to the base of the skull (viewed from behind)

Cervical - related to the neck

Trunk

Thoracic - related to the chest

Sternal - related to the breastbone

Mammary - related to the breasts

Acromial - related to the shoulders

Scapular - related to the shoulder blades

Vertebral - related to the spinal column

Dorsal - related to the back

Abdominal - related to the abdomen

Umbilical - related to the navel

Coxal - related to the hips

Lumbar - related to the lower back

Pelvic - related to the pelvis

Inguinal - related to the groins

Pubic - related to the genital region

Sacral - related to the area between the hips

Gluteal - related to the buttocks

Upper limb

Axillary - related to the armpits

Brachial - related to the arms

Antecubital - related to the front of the elbow (anterior part if viewed in the anatomical position)

Olecranal - related to the back of the elbow

Antebrachial - related to the forearm

Carpal - related to the wrists

Manual - related to the hands

Digital (or phalangeal) - related to the fingers

Palmar - related to the palms of the hqands

Dorsum - related to the back of the hands

Lower limb

Femoral - related to the thighs (vorderer Oberschenkel)

Patellar - related to the anterior knee

Popliteal - related to the area behind the knee

Crural - related to the lower leg

Sural - related to the back of the lower leg (calves, Waden)

Pedal - related to the feet

Tarsal - related to the ankles of the feet

Digital (or phalangeal) - related to the toes

Plantar - related to the sole

Calcaneal - related to the heels

Dorsum - related to the top of the feet

Anatomical directional terms

superior (cephalic, cranial) - towards the upper part

inferior (caudal) - towards the lower part

anterior (ventral) - towards the front

posterior (dorsal) - towards the back

medial - nearer to the midline

lateral - further from the midline

intermediate - between two structures

ipsilateral - on the same side of the body

contralateral - on the opposite side of the body

proximal - nearer to the origin of a structure, especially a limb

distal - further from the origin of a structure, especially a limb

superficial - towards the surface of the body

deep - further from the surface of the body

Planes through the human body:

midsagittal - dividing into left and right along the midline of the body

parasagittal - dividing into left and right, but not along the midline of the body (rather left or right of the midline)

transverse - dividing into upper and lower

frontal - dividing into front and back

oblique - dividing by a slanting plane

Two body cavities:

Dorsal body cavity - the cranial cavity and the vertebral (spinal) canal together form the dorsal cavity; the meninges (three layers of protective tissue) line the dorsal body cavity

Ventral body cavity - the superior, thoracic and the inferior, abdominopelvic cavity together form the ventral body cavity; the diaphragm (a dome-shaped MUSCLE) separates the thoracic and abdominopelvic cavities; all the organs of the ventral cavity together are named “viscera”

Thoracic body cavity (the upper part of the ventral body cavity) - the space of the thoracic cavity that is not occupied by the lungs is named the mediastinum; the mediastinum contains the following organs: the heart (in the pericardial cavity), esophagus, trachea, thymus, blood vessels, etc

Abdominopelvic body cavity (the lower part of the ventral body cavity) - divided into two parts (though no real barrier separates the two portions), the abdominal cavity (with the stomach, spleen, liver, gallbladder, small intestine, and most of the large intestine) and the pelvic cavity (with then urinary bladder, parts of the large intestine, and the internal organs of the reproductive system)

Thin, double-layer, fluid-filled serous membranes compartmentalizes the thoracic and abdominopelvic body cavities. Attention: the spaces between the layers are also called cavities. For example, the pericardial cavity is the cavity BETWEEN the parietal and visceral layers of the pericardium; it is not the space where the heart as a whole is located.

The serous membrane of the pleural cavities is the pleura; the parietal layer of the pleura attaches to the wall of the thoracic body cavity, and the visceral layer lines the lungs.

The serous membrane of the heart is the pericardium; the parietal layer of the pericardium attaches to the wall of the thoracic body cavity, and the visceral layer lines the heart.

perineum - region below the pelvic diaphragm

peritoneum - a serous membrane

The serous membrane of the abdominopelvic cavity is the peritoneum. With its parietal layer, it covers the anterior and lateral abdominopelvic cavity, but in the posterior abdominopelvic cavity, some organs lie between the parietal layer of the peritoneum and the posterior wall of the abdominopelvic cavities. This is the case for the kidneys, adrenal glands, duodenum of the small intestine, ascending and descending colons of the large intestine, parts of the aorta and vena cava. The other viscera of the abdominopelvic cavity are lined by the visceral layer of the peritoneum, while the parietal layer of the peritoneum attaches to the wall of the abdominapelvic cavity.

Abdominopelvic regions

The region is divided either into 9 or 4 parts

If divided into 9 regions, this is done like this: vertical lines are imagined from the midpoint of the clavicles (just medial to the nipples) through the abdomen. These vertical lines result in a wider midsection and a left and a right narrower section.

Horizontal lines are imagined just below the rib cage (subcostal line) and just inferior to the top of the hip bones (transtubercular line).

Parts above the subcostal line, from left to right (when viewed by the observer):

Right hypochondriac region, epigastric region, left hypochondriac region

Parts below the subcostal line (above the transtubercular line), from left to right (when viewed by the observer):

Right lumbar region, umbilical region, left lumbar region

Parts below the transtubercular line, from left to right (when viewed by the observer):

Right inguinal (iliac) region, hypogastric (pubic) region, left inguinal (iliac) region

Medical imaging

Radiography (x-ray) - (clear images of bones which appear in light color; poor images of soft internal organs)

Magnetic resonance imaging (MRI) - uses a high-energy magnetic field, shows fine detail for soft tissues, but not for bones; can detect brain abnormalities and tumors, as well as artery-clogging fatty plaques

Computed tomography (CT) [formerly named computerized axial tomography, CAT] - a kind of x-ray, taken from various angles

Sonography (ultrasound) - safe, noninvasive; primarily used to show fetuses

Positron emission tomography (PET) - injection of a substance that emits positively charged particles (positrons); when they collide with negatively charged particles, they produce gamma rays (similar to x-rays); a PET scan basically shows where in the brain (or other body structure) a lot of activity is taking place

Types of tissue and their origin

4 types of tissue:

1. epithelial (from endoderm, mesoderm, ectoderm)

2. connective (from mesoderm)

3. muscle (from mesoderm)

4. nervous (from ectoderm)

biopsy - the removal of a sample of living tissue for microscopic examination (usually for cancer)

Cell junctions

Tight junctions (common for the linings of internal organs through which materials are channeled, e.g. stomach, intestine, urinary bladder; transmembrane proteins knot cells to each other and avoid that substances enter intracellular space)

Adherens junctions (the formation of adhesion belts between cells; plaques of proteins underneath cell membranes that are “screwed” together by transmembrane glycoproteins called cadherins; the primary function of adherens junctions is providing physical strength, so that adjacent cells cannot be separated)

Desmosomes (desmosomes are similar to adherens junctions in both function and structure; common for epidermis and cardiac muscle; however, they are more like spot wielding between cells, not forming long adhesion belts)

Hemidesmosomes (like desmosomes, but they are not found between equal cells; rather, they anchor cells to a basement membrane)

Gap junctions (these are junctions that provide tiny pipes, named connexons, between the cytoplasm of adjacent cells through which ions and small molecules can be exchanged between cells; the connexons are formed from the protein connexin)

Epithelial tissue

Apical surface of epithelial tissue faces the outer surface of the body, or lines a body cavity or the lumen of organs or an internal duct that receives secretions. The opposite surface is the basal surface.

Epithelial tissue lacks blood supply but is enervated. Nutrients diffuse into epithelial cells from connective tissue below the epithelial tissue.

Epithelial tissue has a high rate of cell division. Damaged or old epithelial cells are sloughed off.

Two kinds of epithelial tissue:

1. Covering (lining) epithelium

2. Glandular epithelium (the secreting portion of glands)

Covering (lining) epithelium

Covering epithelium can come as layers of single or multiple cells. Layers of single cells are referred to as simple epithelium. Layers of multiple cells are called stratified epithelium. There is also pseudostratified epithelium. It looks like stratified because the nuclei are not at a uniform level, and not all cells have apical surfaces.

Glandular epithelium

Glands are either single cells or groups of cells.

Glands are either endocrine or exocrine, or both.

The secretions of endocrine glands are hormones. Hormones enter the interstitial fluid, and from there the blood. No ducts needed.

Goblet cells are unicellular glands that secrete mucus directly onto the apical surface of epithelium, not into ducts

Multicellular exocrine glands secrete their products into ducts that empty through covering epithelium either to the outside of the body, or into the lumen of a hallow organ.

Products of exocrine glands: mucus, sweat, oil, earwax, saliva, and digestive enzymes.

Multicellular exocrine glands can either be tubular (tube-shaped) or acinar (berry-shaped).

Exocrine glands can also be categorized as merocrine (released by exocytosis), apocrine glands (part of the cell that holds the secretion divides from the rest of the cell), or holocrine glands (secretory products accumulate in the cytosol and the cell raptures to release the secretion; example sebaceous glands of the skin).

Connective tissue

Functions of connective tissue: it binds together, supports, and strengthens other tissue; it protects and insulates organs; it compartmentalizes body structures; it stores energy (adipose tissue is a type of connective tissue); blood is also a type of connective tissue; the immune response is also primarily a function of connective tissue.

General features

Connective tissue consists of cells and matrix in between the cells. The matrix is usually formed by the cells. Most connective tissues have rich blood supply and also nerve supply. The matrix of connective tissues is different from place to place, depending on the specific function of connective tissue.

Areolar connective tissue lines joint cavities.

Connective tissue cells

Immature cells of connective tissue are named “-blasts” (fibroblasts for loose and dense connective tissue, chondroblasts for cartilage, osteoblasts for bones).

Blast cells can divide and they secrete the matrix. When the cells mature (then named “-cytes”) they no longer easily divide and no longer secrete matrix, but have a role in the maintenance of the matrix.

Some connective tissue cells:

Fibroblasts - among the most common connective tissue cells; they secrete the fibers and ground substances of the matrix

Macrophages - they develop from monocytes (a type of white blood cells); there are fixed macrophages and wandering macrophages

Plasma cells - they develop from white blood cells called B lymphocytes and secrete antibodies; they are found in many places of the body but are most common in connective tissue (especially the GI and the respiratory tract)

Mast cells - most common near blood vessels; they produce histamine, which deletes blood vessels; histamine plays an important role in inflammations

Adipocytes - fat cells that store triclycerides; common below the skin and around internal organs

White blood cells - not normally in connective tissue, but neutrophils (infections) and eosinophils (parasites, allergies) accumulate during problems

Connective tissue matrix

Matrix consists of fluid, semifluid, gelatinous, or calcified ground substance, and protein fibers

Ground substance

Ground substance consists of water and an assortment of large molecules, many of which are combinations of polysaccharides and proteins.

Polysaccharides in matrix - glycosaminoglycans (GAGs)

Proteins in matrix - proteoglycans

In combinations, the proteogycans form the cores and the GAGs project like the bristles of a brush; this shape assures that the matrix traps water and becomes jellylike.

Hyaluronic acid - a viscious, slippery substance that binds cells together, lubricates joints, and helps maintain the shape of the eyeball; white blood cells, sperm cells, and some bacteria produce the enzyme hyaluronidase, which dissolves hyaluronic acid and makes it watery and less resitant

Fibronectins - adhesion proteins that bind ground substance and collagen fibers

Fibers

Three kinds of fibers in connective tissue: collagen fibers, elastic fibers, reticular fibers

Collagen fibers are made of the protein collagen, which is the most abundant protein in the human body, accounting for some 25 % of all proteins. Collagen fibers often lie in parallel bundles’ they provide strength to the tissue.

Elastic fibers form networks; they are made from the protein elastin, which is surrounded by the glycoprotein fibrillin. Elastic fibers can be stretched up to 150 % and will return to their original form when the stretching subsides. Elastic fibers are important in skin and in blood vessels.

Reticular fibers are also made of collagen, but they are not bundled but rather form networks of thin fibers; reticular fibers are plentiful in the stroma (the supporting framework of sift organs; they also are an essential feature of the basement membrane

Marfan syndrome - an inherited disorder caused by a defective fibrillin gene

Classification of connective tissue

Main classification:

Embryonic and mature connective tissue

Embryonic connective tissue is subdivided only into two subtypes: mesenchyme and mucous connective tissue. All other connective tissue eventually arises from mesenchyme. Mucous connective tissue is found mainly in the umbilical cord.

There are six types of mature connective tissue:

1. loose connective tissue (areolar, adipose, reticular)

2. dense connective tissue (regular, irregular, elastic)

3. cartilage (hyaline, fibro-, elastic)

4. bone (details chapter 6)

5. blood (details chapter 19)

6. lymph (details chapter 22)

Loose connective tissue

Areolar connective tissue - semifluid; under the skin, around blood vessels, nerves, and internal organs

Adipose connective tissue - fat cells; reduces heat loss, stores energy; under the skin, padding around joints and behind the eyeball, yellow bone marrow; brown adipose tissue in newborns generates heat (in mitochondria) to maintain body temperature

Reticular connective tissue - stroma (supporting framework) of liver, spleen, and lymph nodes; binds smooth muscle cells; filters blood in spleen (for worn out cells) and lymph in lymph nodes (for microbes)

Dense connective tissue

Dense connective tissue contains more fiber, but fewer cells than loose connective tissue

Dense regular connective tissue - consists mainly of collagen fibers in bundles; forms ligaments, tendons, and aponeuroses (sheetlike tendons between muscle and muscle or muscle and bone)

Dense irregular connective tissue - also consists mainly of collagen fibers, but they are not arranged in bundles as is dense regular connective tissue; found in areas in which the pull is not primarily in a specific direction (as it is for tendons and ligaments); forms fascia (tissue beneath skin and around muscles);

Elastic connective tissue - this connective tissue allows the stretching of organs; it is found in the lungs and the walls of elastic arteries;

Cartilage

Cartilage is a dense network of collagen fibers in chondroitin sulfate which is stronger than loose or dense connective tissue. Cartilage grows slowly, and tissue repair is also slowly. This is the case because cartilage is avascular.

During childhood and adolescence, cartilage grows interstitially; this means that the chondrocytes divide and produce cartilage, expanding the cartilage from within.

In appositional growth, cartilage growth is effected by fibroblasts in the perichondrium some of which differentiate into chondroblasts, then chondrocytes; they add cartilage to the outer surface of the cartilage.

Hyaline cartilage - the most abundant cartilage; bluish-white; fine collagen fibers and plenty of chondrocytes; forms the skeleton of embryos and fetuses; in adults: ends of long bones, nose, parts of larynx, trachea, bronchial tubes.

Fibrocartilage - forms intervertebral discs, menisci (cartilage of the knee pads); consists of collagen bundles with chondrocytes

Elastic cartilage - the auricle (external ear), Eustachian (auditory) tubes; consists of chondrocytes in networks of elastic fibers

Bones are a type of connective tissue that will be discussed in a separate file.

Membranes

Epithelial membranes are a combination of an epithelial layer and a connective tissue layer.

Synovial membranes (that line joints) consist of connective tissue only.

Epithelial membranes

The skin is a stratified squamous epithelial membrane which will be discussed in a separate file.

Mucous membranes line surfaces that open to the outside, such as the entire GI tract, the respiratory and reproductive tracts, and much of the urinary tract.

Goblet cells in the epithelial layer of mucous membranes secrete mucus which provides a barrier against microbes, and smoothes the passage of food, lubricates, and prevents the membrane from drying out. The epithelial layer of the GI mucous membrane also secretes enzymes and allows the absorption of nutrients.

The connective tissue layer of mucous membranes consists of areolar connective tissue and is called lamina propria. The lamina propria binds the epithelial layer of a mucous membrane to the underlying structure and delivers oxygen and absorbs carbon dioxide (epithelial tissue is avascular… it does not have its own blood supply; connective tissue has ample blood supply).

Serous membranes line body cavities that do not open to the outside and cover internal organs within the cavity. Serous membranes have two layers, the (outer) parietal layer that lines the cavity, and the (inner) visceral layer that covers the organ. Serous membranes consist of areolar connective tissue and simple squamous epithelium (mesothelium), which secretes serous fluid. The serous fluid lubricates and allows the organs to slide against each other or along the internal cavities.

Pleura - the serous membrane lining the thoracic cavity and covering the lungs

Pericardium - the serous membrane of the heart

Peritoneum - the serous membrane lining the abdominal cavity and and covering abdominal organs

Synovial membranes

Synovial membranes line the cavities of freely movable joints; they are composed of areolar connective tissue with adipocytes and elastic fibers. Articular synovial membranes secrete synovial fluid to nourish and lubricate the cartilage of joints. Synovial membranes also line tendon sheaths in the hands and feet.

Muscle tissue

Skeletal muscle tissue consists of long cells called muscle fibers. Each has many nuclei located at the periphery of the cell. Skeletal muscle is striated. The muscle fibers in a single muscle lie parallel to each other.

Cardiac muscle cells are also striated. They are branched and normally have only one nucleus. Cardiac muscle cells are attached to each other end-to-end by intercalated discs (traverse thickening of plasma membranes). The intercalated discs connect the muscle cells both through desmosomes and gap junction. The desmosomes provide strength, and the gap junctions allow the conduction of muscle action potentials from cell to cell.

Smooth muscle tissue is not striated, and there is only one nucleus per cell. Smooth muscle tissue forms the walls of hallow internal organs such as blood vessels, airways to the lungs, stomach, intestines, gallbladder, urinary bladder.

More on muscle tissue in a separate file.

Nervous tissue

Nervous tissue will be discussed in a separate file.

Tissue repair

Stroma - supporting connective tissue

Parenchyma - cells of the functioning part of a tissue or organ

Epithelial tissue has a continuous capacity for renewal. Epithelial stem cells reside in protected areas of the skin and the GI tract.

Stem cells in red bone marrow continually provide new red and white blood cells and platelets. Bone also can replenish lost cells.

Muscle tissue has a poor capability for renewal. There are a few muscle stem cells in skeletal muscle, called satellite cells, but their rate of renewal is slow. Heart muscle also has only a very limited capacity for renewal, though it lacks satellite cells; stem cells for heart muscle are delivered by the blood from red bone marrow. Smooth muscle also only has a limited capacity for renewal; it’s not as good as the capacity of connective tissue, but better than that of skeletal muscle tissue.

Nervous tissue practically does not regenerate.

If parenchymal cells achieve tissue repair, the repair site will be functional; if the repair is handled by stroma, then connective tissue will grow instead of whatever the original tissue was, and a scar will show. The process of scaring = fibrosis.

Granulation tissue - replaced tissue, including replaced blood vessels

Nutrition important for wound healing, especially protein; vitamin C is also needed.

Aging and tissue

In the young, tissue heals faster. In fetuses, surgery leaves no scars.

A negative effect of glucose with aging: within and outside cells, glucose causes irreversible links between protein, which then loose elasticity of aging tissue. Loss of elasticity is also caused by an increase of collagen and the affinity for calcium of elastin.

Disorders

Autoimmune diseases such as rheumatoid arthritis (attacks synovial membranes of joints) are the most common tissue disorders.

Sjoegren’s Syndrome - autoimmune disorder causing inflammation and destruction of exocrine glands, especially lacrimal (tear) glands and salivary glands; can manifest itself as pancreatitis, pleuritis, and migraine. Affects females nine times more than males.

Systemic lupus erythematosus - an autoimmune tissue disease; chronic connective tissue inflammation most common in non-white women of childbearing age. Can be mild or even fatal. Females nine times more often affected. Exact causes unknown, but may be estrogen-triggered. No treatment. Often with a rush on the cheeks across the nose (butterfly rush).

Medical terminology

Atrophy - a decrease in the size of cells, with a subsequent decrease in the size of a tissue

Hypertrophy - an increase in tissue size because cells grow in size without becoming more numerous

Tissue rejection - an immune response against foreign proteins

Tissue transplantation - best if a body’s own tissue can be used