Lymphatic System lymph Lymphatic system has a particular value in the judgment of the slaughter animal. The inspection of the lymph nodes for the presence of pathological lesions lies in the fact that mainly due to the rapid response of the lymph node to an irritant with enlargement and congestion of its substance and possible breaking down of its tissue. Thus, the size, colure and consistency of lymph nodes form a valuable guide in the establishment of diseases processes in the animal body. Lymph node consists of reticular frame work of elastic and smooth muscle fibers enclosing lymphatic tissue which contains lymphocytes. The lymphatic vessel which conveying lymph to lymph node are known as Afferent. The area drained by the particular lymph node is known as Drainage area. An appreciation of the drainage areas of lymph nodes is important in the judgment of septic infections and tuberculous carcass. The lymph after passing through one more lymph node and there by ridding itself of some impurities, lymph is conveyed by efferent lymph collecting vessels. The direction of lymph flow being toward the heart. Functions of lymph node Lymph circulation Features of lymph nodes a) Size b) Shape c) Colure d) Consistency Features of lymph nodes a-Size The size of lymph nodes varies from that of a pinhead up to hen egg. However, the posterior mediastinal lymph node of cattle may reach a length of 25 cm. the size of lymph nodes is relatively greater in the young growing animal than adult, this may be attributed to a relatively greater growth intensity of lymphatic tissues. In the horse, the nodes are small and occur in large in number forming grape- like group. Whilst in ruminates they consist of a few glands of large size only. In older animals the nodes are smaller than younger animal. Features of lymph nodes b-Shape The shape of lymph nodes are generally round or oval and some what compressed. In ruminants they are large and few in numbers. While lymph node of pigs are lobulated and superficial lymph node in camel (prepectoral and superficial inguinal) are lobulated. On incision a small quantity of lymph exudate. Features of lymph nodes c-Colure The colure of lymph nodes showed considerable variation and may be white, greyish blue, or almost black. The mesenteric lymph nodes of cattle are constantly black. The lymph nodes of the pigs are lobulated and almost white, with exception of those of the head and neck which are reddish. Red colure varying degree of hyperemia Yellow colure fatty infiltration and is often met within the mesenteric lymph nodes. Green colure eosinophilia caused by parasitic invasion in the drainage area. Gray or black colures particles of dust brought to the lymph nodes through afferent lymphatic vessels especially bronchial lymph known as anthracnose. Lymph nodes of Cattle Lymph nodes of Head 1-Submaxillary or mandibular lymph node 2-Parotid lymph node 3-Retrpharynegeal lymph node 3A-Medial retropharyngeal lymph node (Supra- paryngeal lymph node) 3B-lateral retropharyngeal lymph node (Atlantal lymph node) Lymph nodes of Head and Neck 1-Submaxillary or mandibular lymph node P: one on each side just inside angel of the jaw and embedded in the fat it reach 2-4.5 cm in length D: muscle and skin of the head, nasal cavity hard and soft gum and tongue (Head, nose and mouth) E: lateral retropharyngeal lymph node which is important in meat inspection. 2-Parotid lymph node (one each side): Its flat node 7.5 cm long by 2.5 cm wide, and showed always be examined in old cows. P:one on each side , on the edge of the masseter muscle and covered by the parotid salivary gland which must be incised to expose it. D: skin of the head, master muscle, head bones, anterior part of nasal cavity hard and soft gum , ear, parotid gland and cranial cavity(Muscle of head, eye, ear, tongue and cranial cavity) E: lateral retropharyngeal nodes. 2-Parotid lymph node (one each side): Its flat node 7.5 cm long by 2.5 cm wide, and showed always be examined in old cows. P:one on each side , on the edge of the masseter muscle and covered by the parotid salivary gland which must be incised to expose it. D: skin of the head, master muscle, head bones, anterior part of nasal cavity hard and soft gum , ear, parotid gland and cranial cavity(Muscle of head, eye, ear, tongue and cranial cavity) E: lateral retropharyngeal nodes. 3B-Lateral retropharyngeal lymph node: P: situated beneath each wing of the atlas (first cervical vertebra) and therefore are usually located at the neck of the dressed carcass. D: tongue, salivary gland, hyoid , cervical and master muscles and receive efferent vessels from the submaxillary parotid and medial retropharyngeal( tongue and receive efferent from submaxillary, parotid and internal retropharyngeal nodes) E: tracheal lymph ducts Lymph nodes of the neck 1-Superficl cervical lymph node 1a-Anterior superficial cervical lymph node 1b-posterior superficial cervical or prescapular lymph node 2-Deep cervical lymph node 2a-Anterior deep cervical lymph node 2b-Middle deep cervical lymph node 2c-Posterior deep cervical (Prepectoral lymph node) 2d-Cost-cervical Posterior superficial cervical or prescapular lymph node Posterior superficial cervical or prescapular lymph node: P: An elongated lymph node 7-9 cm in length and 2.5cm or more in width. It lies anterior to and slightly above the shoulder joint (or situated at the anterior border of the supraspinatus muscle) deep incision 15cm long and 5cm deep must be made to expose it , node is embedded in fat (It expose by cutting an incision parallel to the shoulder in the superficial muscles ) It is exposure is greatly facilitated if the carcass is examined before the onset of rigor mortis. D: Skin of the neck , shoulder and part of thorax , scapular muscle, tendons and muscles of the forelimb and joints of shoulder, carpus and digit (Neck, shoulder ,and forelimb including bones and muscles) E: on the right side it open into the end of the tracheal duct, while those of left side open into terminal part of the thoracic duct of anterior vena cava. Lymph nodes of the neck 1-Superficl cervical lymph node 1a-Anterior superficial cervical lymph node 1b-posterior superficial cervical or prescapular lymph node 2-Deep cervical lymph node 2a-Anterior deep cervical lymph node 2b-Middle deep cervical lymph node 2c-Posterior deep cervical (Prepectoral lymph node) 2d-Cost-cervical Anterior group: P: are situated along the anterior part of the trachea, 4-6 small lymph nodes in number and found in the region of the thyroid region. D: ventral part of the skin of the neck, pharyngeal muscles, larynx, salivary gland, esophagus , trachea and thyroid glands. E: tracheal ducts Middle group: P: are often absent and when present are situated in the middle third of the neck on each side of trachea. D: ventral muscles of the neck, esophagus, larynx, trachea and cervical part of the thymus, prepectoral lymph node, cost-cervical , axillary and prescapular. E: tracheal duct. Posterior group Prepectoral lymph node Costocervical lymph node Prepectoral lymph node Prepectoral lymph node: P: two to four nodes on each side and are embedded in fat along the anterior border of the first rib. The main node of this group is superficially situated about the middle of the first rib and just anterior to it. The second node of this group is on the same level and just anterior to the main node but is deep-seated and is exposed by making an incision 10 cm long and 5 cm deep through the triangular-shaped scalenus muscle . (Prepectoral 2-4 lymph nodes on each side embedded in fat along the anterior border of first rib). Haemal lymph nodes are usually present in the fat around this group. D: Efferent from lateral retropharyngeal , prescapular and axillary nodes, thus all lymph from the head and neck passes through the prepectoral lymph node besides that from the forequarter. E: thoracic duct Costocervical lymph node Cost cervical lymph nodes: P: this may be found on the inner side or just anterior to the first rib and close to its junction with the first thoracic vertebra . It lies adjacent to the esophagus and trachea and is frequently removed with theses during dressing of the carcass. This lymph node is regarded as a connecting link between the cervical and mediastinal lymph node as it receive lymph from both cervical region and pleura. D: Neck, shoulder, partial pleura, and first few intercostal nodes. E: on the right side usually discharge into the right tracheal duct, while on the left side discharge into the end of thoracic duct. Axillary (brachial) lymph node P: between the scapula and the space between the 1st and 2nd ribs about mid-way between the vertebral column and sternum. This node is about 2.5 cm in length, is covered by the scapula and is situated in the muscle external to and about the midway along the second rib. This lymph node can exposed either from: A-the lateral side, through an incision behind the shoulder with excision of the fat lying between the latissimus dorsi and pectoral muscle. B-the medial side, by severing the intercostal muscle from the first to the second intercostal space, the fat with the node is searched and removed through this opening. D: bones , muscle and joints of the proximal part of the forelimb E: prepectoral lymph node. Lymph nodes of Thorax 1-Intercostal lymph node 2-Sternal lymph node 3-Mediastinal lymph node 4-Bronchail lymph node 1-Intercostal lymph node Intercostal lymph node P: 2.4 cm in diameter are situated in the intercostal spaces at the junction of the ribs with their vertebrae, and are deep – seated being covered by the intercostal muscle, most of these nodes are small and not all spaces contain nodes D: muscles of dorsal region, intercostal muscles, ribs, partial pleura, thoracic wall and peritoneum E: Mediastinal lymph node.