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Human Anatomy & Histology

50. Internal organs.  basic structure.

An organ or viscus is a collection of tissues joined in a structural unit to serve a common function. In anatomy, a viscus is an internal organ, and viscera is the plural form

Organs are composed of main tissue, parenchyma, and “sporadic” tissues, stroma. The main tissue is that which is unique for the specific organ, such as the myocardium, the main tissue of the heart, while sporadic tissues include the nerves, blood vessels, and connective tissues. Functionally related organs often cooperate to form whole organ systems. Organs exist in all higher biological organisms, in particular they are not restricted to animals, but can also be identified in plants. In single-cell organisms like bacteria, the functional analogue of an organ is called organelle.

A hollow organ is a visceral organ that forms a hollow tube or pouch, such as the stomach or intestine, or that includes a cavity, like the heart or urinary bladder.

Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system. The functions of organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamus. For this reason, the two systems are combined and studied as the neuroendocrine system. The same is true for the musculoskeletal system because of the relationship between the muscular and skeletal systems.

Mammals such as humans have a variety of organ systems. These specific systems are also widely studied in human anatomy.

Cardiovascular system: pumping and channeling blood to and from the body and lungs with heart, blood and blood vessels.

Digestive system: digestion and processing food with salivary glands, esophagus, stomach, liver, gallbladder, pancreas, intestines, colon, rectum and anus.

Endocrine system: communication within the body using hormones made by endocrine glands such as the hypothalamus, pituitary gland, pineal body or pineal gland, thyroid, parathyroids and adrenals, i.e., adrenal glands.

Excretory system: kidneys, ureters, bladder and urethra involved in fluid balance, electrolyte balance and excretion of urine.

Lymphatic system: structures involved in the transfer of lymph between tissues and the blood stream, the lymph and the nodes and vessels that transport it including the Immune system: defending against disease-causing agents with leukocytes, tonsils, adenoids, thymus and spleen.

Integumentary system: skin, hair and nails.

Muscular system: movement with muscles.

Nervous system: collecting, transferring and processing information with brain, spinal cord and nerves.

Reproductive system: the sex organs, such as ovaries, fallopian tubes, uterus, vagina, mammary glands, testes, vas deferens, seminal vesicles, prostate and penis.

Respiratory system: the organs used for breathing, the pharynx, larynx, trachea, bronchi, lungs and diaphragm.

Skeletal system: structural support and protection with bones, cartilage, ligaments and tendons.

51. digestive system. gen principles of construction and ontogenesis.

The gastrointestinal wall surrounding the lumen of the gastrointestinal tract is made up of four layers of specialized tissue – from the lumen outwards:

Mucosa.

Submucosa.

Muscular layer.

Serosa

Mucosa

The mucosa is the innermost layer of the gastrointestinal tract. It surrounds the lumen of the tract and comes into direct contact with digested food (chyme). The mucosa itself is made up of three layers: 

The epithelium is the innermost layer. It is where most digestive, absorptive and secretory processes occur.

Lamina propria is a layer of connective tissue within the mucosa. Unusually cellular compared to most connective tissue

Muscularis mucosae is a thin layer of smooth muscle.

Epithelium

The mucosae are highly specialized in each organ of the gastrointestinal tract to deal with the different conditions. The most variation is seen in the epithelium

In the oesophagus, pharynx and external anal canal the epithelium is stratified, squamous and non-keratinizing, for protective purposes.

In the stomach, the epithelium is simple columnar, and is organized into gastric pits and glands to deal with secretion

In the small intestine, epithelium is simple columnar and specialized for absorption. The epithelium is arranged into villi, creating a brush border and increasing the area for absorption. Each cell also has microvilli. it is organized into plicae circulares and villi, and the enterocytes have microvilli. This creates a brush border which greatly increases the surface area for absorption. The epithelium is simple columnar with microvilli. In the ileum there are occasionally Peyer’s patches in the lamina propria. Brunner’s glands are found in the duodenum but not in other parts of the small intestine

In the colon, epithelium is simple columnar and without villi. Goblet cells, which secrete mucous, are also present

The appendix has a mucosa resembling the colon but is heavily infiltrated with lymphocytes.

Transition between the different types of epithelium occurs at the junction between the oesophagus and stomach, between the stomach and duodenum, between the ileum and caecum, and at the pectinate line of the anus

Submucosa

Main article: Submucosa

The submucosa consists of a dense and irregular layer of connective tissue with blood vessels, lymphatics, and nerves branching into the mucosa and muscular layer. It contains the submucous plexus, and enteric nervous plexus, situated on the inner surface of the muscular layer

Muscular layer

Main article: Muscular layer

The muscular layer (also known as the muscularis propria ) consists of two layers of muscle, the inner and outer layer. The muscle of the inner layer is arranged in circular rings around the tract, whereas the muscle of the outer layer is arranged longitudinally. The stomach has an extra layer, an inner oblique muscular layer between the two muscle layers is the myenteric or Auerbach’s plexus. This controls peristalsis. Activity is initiated by the pacemaker cells (interstitial cells of Cajal). The gut has intrinsic peristaltic activity (basal electrical rhythm) due to its self-contained enteric nervous system. The rate can of course be modulated by the rest of the autonomic nervous system.

The layers are not truly longitudinal or circular, rather the layers of muscle are helical with different pitches. The inner circular is helical with a steep pitch and the outer longitudinal is helical with a much shallower pitch.

The coordinated contractions of these layers are called peristalsis and propels the food through the tract. Food in the GI tract is called a bolus (ball of food) from the mouth down to the stomach. After the stomach, the food is partially digested and semi-liquid, and is referred to as chyme. In the large intestine the remaining semi-solid substance is referred to as feces. The circular muscle layer prevents food from travelling backward and the longitudinal layer shortens the tract.

The thickness of the muscular layer varies in each part of the tract:

In the colon, for example, the muscular layer is much thicker because the faeces are large and heavy and require more force to push along. The outer longitudinal layer of the colon thins out into 3 discontinuous longitudinal bands, known as taeniae coli (bands of the colon). This is one of the 3 features helping to distinguish between the large and small intestine.

Occasionally in the large intestine (2-3 times a day) there will be mass contraction of certain segments, moving a lot of faeces along. This is generally when one gets the urge to defecate.

The pylorus of the stomach has a thickened portion of the inner circular layer: the pyloric sphincter. Alone among the GI tract, the stomach has a third layer of muscular layer. This is the inner oblique layer and helps churn the chyme in the stomach.

Serosa/Adventitia

Main articles: Serosa and Adventitia

The outermost layer of the GI tract consists of several layers of connective tissue and is either adventitia or serosa.

Intraperitoneal regions of the digestive tract (aka those parts suspended by peritoneum) are covered with serosa. This structure consists of connective tissue covered by a simple squamous epithelium, called the mesothelium, which reduces frictional forces during digestive movements. The intraperitoneal regions include most of the stomach, first part of the duodenum, all of the small intestine, caecum and appendix, transverse colon, sigmoid colon and rectum. In these sections of the gut there is clear boundary between the gut and the surrounding tissue. These parts of the tract have a mesentery.

Retroperitoneal regions of the digestive tract (aka those parts that are firmly attached to surrounding structures by connective tissue fibers) parts are covered with adventitia. They blend into the surrounding tissue and are fixed in position (for example, the retroperitoneal section of the duodenum usually passes through the transpyloric plane). The retroperitoneal regions include the oral cavity, esophagus, pylorus of the stomach, distal duodenum, ascending colon, descending colon and anal canal.

The gut is an endoderm-derived structure. At approximately the 16th day of human development, the embryo begins to fold ventrally (with the embryo’s ventral surface becoming concave) in two directions: the sides of the embryo fold in on each other and the head and tail fold toward one another. The result is that a piece of the yolk sac, an endoderm-lined structure in contact with the ventral aspect of the embryo, begins to be pinched off to become the primitive gut . The yolk sac remains connected to the gut tube via the vitelline duct. Usually this structure regresses during development. In cases where it does not, it is known as Meckel’s diverticulum.

Development of Digestive System

Sagittal section of embryo at about four weeks showing the primitive gut.

During fetal life, the primitive gut can be divided into three segments: foregut, midgut, and hindgut. Although these terms are often used in reference to segments of the primitive gut, they are also used regularly to describe components of the definitive gut as well. Each segment of the gut gives rise to specific gut and gut-related structures in later development. Components derived from the gut proper, including the stomach and colon, develop as swellings or dilatations of the primitive gut. In contrast, gut-related derivatives (that is, those structures that derive from the primitive gut, but are not part of the gut proper), generally develop as outpouchings of the primitive gut. The blood vessels supplying these structures remain constant throughout development. The foregut is the esophagus to first two sections of the duodenum, liver, gallbladder, and superior portion of pancreas. The midgut is the lower duodenum, to the first two-thirds of the transverse colon lower duodenum, jejunum, ileum, cecum, appendix, ascending colon, and first two-thirds of the transverse colon. The hindgut is the last third of the transverse colon, descending colon, rectum, and upper part of the anal canal.

52. oral cavity- parts. ontogenesis. anomalies.

The oral cavity includes the lips, the inside lining of the lips and cheeks (buccal mucosa), the teeth, the gums, the front two-thirds of the tongue, the floor of the mouth below the tongue, and the bony roof of the mouth (hard palate).

Following the tearing of the oropharyngeal membrane in the young embryo, the ectoderm-covered stomodeum, which gets surrounded by the mandibular prominences, goes directly over into the endoderm-covered foregut. It is also called a primary oral cavity because at this time no nasal cavity yet exists. (For the forming of the exterior nose, see facial development).

Only through the formation of the nasal sacs are the primary palates (=floors of the two nasal sacs) formed that divide the primary oral cavity into oral and nasal cavities. The wall between the two nasal sacs is called the nasal septum.

The adenohypophysial primordium (AH) appears in stage 10 (28 days) in front of the oropharyngeal membrane as thickening of the ectoderm. It develops in the immediate vicinity of the basal plate of the neural tube (prosencephalon [forebrain]).

At the same time, a sacculation arises from this part of the basal plate, the neurohypophysis (NH). This basal plate belongs to the future diencephalon (part of the prosencephalon). The AH primordium forms a pouch (Rathke’s pouch) in stage 13 (32 days), which remains in constant contact with the NH of the diencephalon and later surrounds this in the front.

Subsequently, the AH loses the contact to the ectoderm and, through further embryonic flexion and the expansion of the prosencephalon (= future di- and telencephalon) gets displaced at the cerebral base together with the NH. 

With the facial formation through the spreading maxillar and mandibular arches the AH orifice is displaced into the pharynx roof. The skull base (os sphenoideum) forms between the pharynx roof and the AH in the later embryonic period.

Cleft lip and cleft palate, also known as orofacial cleft and cleft lip and palate, is a group of conditions that includes cleft lip (CL), cleft palate (CP), and both together (CLP). A cleft lip contains an opening in the upper lip that may extend into the nose. The opening may be on one side, both sides, or in the middle. A cleft palate is when the roof of the mouth contains an opening into the nose. These disorders can result in feeding problems, speech problems, hearing problems, and frequent ear infections. Less than half the time the condition is associated with other disorders.

Cleft lip and palate are due to tissues of the face not properly joining together during development. They are a type of birth defect. The cause in most cases is unknown.[1] Risk factors include smoking during pregnancy, diabetes, an older mother, obesity, and certain medications such as some used to treat seizures, they can often be diagnosed during an ultrasound done during pregnancy.

A cleft lip or palate can be successfully treated with surgery. This is often done in the first few months of life for cleft lip and before eighteen months for cleft palate. Speech therapy and dental care may also be needed. With appropriate treatment outcomes are good

53. ORAL cavity vestibule. oral cavity proper. lips and cheeks

The mouth consists of two regions, the vestibule and the oral cavity proper. The vestibule is the area between the teeth, lips and cheeks.[2] The oral cavity is bounded at the sides and in front by the alveolar process (containing the teeth) and at the back by the isthmus of the fauces. Its roof is formed by hard palate and soft palate and the floor is formed by the mylohyoid muscles and is occupied mainly by the tongue. Mucous membrane lines the sides and under surface of the tongue to the gum lining the inner aspect of the jaw mandible. It receives the secretions from the submaxillary and sublingual salivary glands.

Divisions of the Oral Cavity

The oral cavity spans between the oral fissure (anteriorly – the opening between the lips), and the oropharyngeal isthmus (posteriorly – the opening of the oropharynx).

It is divided into two parts by the upper and lower dental arches (formed by the teeth and their bony scaffolding). The two divisions of the oral cavity are the vestibule, and the mouth cavity proper.

Vestibule

The horseshoe-shaped vestibule is situated anteriorly. It is the space between the lips/cheeks, and the gums/ teeth.

The vestibule communicates with the mouth proper via the space behind the third molar tooth, and with the exterior through the oral fissure. The diameter of the oral fissure is controlled by the muscle of facial expression – principally the orbicularis oris.

Opposite the upper second molar tooth, the duct of the parotid gland opens out into the vestibule, secreting salivatory juices.

Mouth Proper

The mouth proper lies posteriorly to the vestibule. It is bordered by a roof, a floor, and the cheeks. The tongue fills a large proportion of the cavity of the mouth proper.

The Roof

The roof of the mouth proper consists of the hard and soft palates.

The hard palate is found anteriorly. It is a bony plate that separates the nasal cavity from the oral cavity. It is covered superiorly by respiratory mucosa (pseudostratified squamous epithelium) and inferiorly by oral mucosa (stratified squamous epithelium).

The soft palate is a posterior continuation of the hard palate. In contrast to the hard palate, it is a muscular structure. It acts as a valve that can lower to close the oropharyngeal isthmus and elevate to separate the nasopharynx from the oropharynx.

The Floor 

The floor of the oral cavity consists of several structures:

Muscular diaphragm – comprised of the bilateral mylohyoid muscles. It provides structural support to the floor of the mouth and pulls the larynx forward during swallowing.

Geniohyoid muscles – pull the larynx forward during swallowing.

Tongue – connected to the floor by the frenulum of the tongue, a fold of oral mucosa.

Salivary glands and ducts.

The Cheeks

The cheeks are formed by the buccinator muscle, which is lined internally by the oral mucous membrane

The buccinator muscle contracts to keep food between the teeth when chewing and is innervated by the buccal branch of the facial nerve (CN VII).

he upper and lower lips are referred to as the “Labium superius oris” and “Labium inferius oris”, respectively. The juncture where the lips meet the surrounding skin of the mouth area is the vermilion border, and the typically reddish area within the borders is called the vermilion zone. The vermilion border of the upper lip is known as the cupid’s bow.[5] The fleshy protuberance located in the center of the upper lip is a tubercle known by various terms including the procheilon (also spelled prochilon), the “tuberculum labii superioris”, and the “labial tubercle”. 

The vertical groove extending from the procheilon to the nasal septum is called the philtrum Innervation

Sensory innervation of the oral cavity is supplied by the branches of the trigeminal nerve (CN V)

The hard and soft palates are innervated by the greater palatine and nasopalatine nerves. They are both derived from the maxillary branch (V2) of the trigeminal nerve.

The floor of the oral cavity receives sensory innervation from the lingual nerve – a branch of the mandibular (V3) division of the trigeminal nerve. The tongue is also innervated by special sensory fibres for taste from the chorda tympani, a branch of the facial nerve (CN VII)

The cheeks are innervated by the buccal nerve. It is also a branch of the mandibular division of the trigeminal nerve.

54. oral cavity. soft and hard palate and oral mucosa.

The soft palate (also known as velum or muscular palate) is, in mammals, the soft tissue constituting the back of the roof of the mouth. The soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone.

The five muscles of the soft palate, play important roles in swallowing and breathing. The muscles are:

Tensor veli palatini, which is involved in swallowing

Palatoglossus, involved in swallowing

Palatopharyngeus, involved in breathing

Levator veli palatini, involved in swallowing

Musculus uvulae, which moves the uvula

These muscles are innervated by the pharyngeal plexus via the vagus nerve, with the exception of the tensor veli palatini. The tensor veli palatini is innervated by cranial nerve 5 branch V3 (which is the mandibular division of the trigeminal cranial nerve).[2]

The hard palate is a thin horizontal bony plate of the skull, located in the roof of the mouth. It is formed by the palatine process of the maxilla and horizontal plate of palatine bone, and spans the arch formed by the upper teeth.

The hard palate is formed by the palatine process of the maxilla and horizontal plate of palatine bone. It forms a partition between the nasal passages and the mouth. On the anterior portion of the roof of the hard palate are the rugae, irregular ridges in the mucous membrane that help facilitate the movement of food backwards towards the pharynx. This partition is continued deeper into the mouth by a fleshy extension called the soft palate.

the oral mucosa is the mucous membrane lining the inside of the mouth and consists of stratified squamous epithelium termed oral epithelium and an underlying connective tissue termed lamina propria.

Oral mucosa consists of two layers, the surface stratified squamous epithelium and the deeper lamina propria. In keratinized oral mucosa, the epithelium consists of four layers:

Stratum basale (basal layer)

Stratum spinosum (prickle layer)

Stratum granulosum (granular layer)

Stratum corneum (keratinized layer)

In nonkeratinized epithelium, the two deep layers (basale and spinosum) remain the same, but the outer layers are termed the intermediate and superficial layers.

Depending on the region of the mouth, the epithelium may be nonkeratinized or keratinized. Nonkeratinized squamous epithelium covers the soft palate, inner lips, inner cheeks, and the floor of the mouth, and ventral surface of the tongue. Keratinized squamous epithelium is present in the attached gingiva and hard palate as well as areas of the dorsal surface of the tongue.[4][5]

Keratinization is the differentiation of keratinocytes in the stratum granulosum into nonvital surface cells or squames to form the stratum corneum. The cells terminally differentiate as they migrate to the surface from the stratum basale where the progenitor cells are located to the superficial surface.