獸醫(yī)產(chǎn)科學5

1、獸醫(yī)產(chǎn)科學Veterinary Obstetrics(Theriogenology),內(nèi) 蒙 古 農(nóng) 業(yè) 大 學獸醫(yī)學院College of Veterinary Science Inner Mongolia Agriculture University劉 俊 平 LIU Jun-pingTel: 4308539 13848137992 E-mail: LiuJP8539@163.com,第 五 章 分

2、 娩 Parturation,Parturition or labor 孕畜經(jīng)過正常的懷孕期滿(胎兒發(fā)育成熟)，母體將胎兒及其附屬物從子宮排出體外的生理過程，叫分娩。 瓜熟蒂落 What is Parturition?Act of process of giving birth,2024/3/26,2,2011,3,Average length of gestation,*Average varies wit

3、h animals and breeds.,2024/3/26,2011,4,*Average varies with animals and breeds.,Average length of gestation,2024/3/26,2011,Parturition and Labor:,The time an embryo or fetus is carried in the uterus is called gestation.

4、Parturition refers to birth and is accompanied by a sequence of events called labor. The birth of a baby involves dilation of the cervix, expulsion of the fetus, and delivery of the placenta.,2024/3/26,5,2011,不同動物分娩名稱

5、Parturition Names in Species,Cattle: CalvingSheep:LambinggoatkiddingSwine:FarrowingHorse: FoalingCat: Kittening Dog: Whelping,2024/3/26,6,2011,第 五 章 分 娩 Parturat

6、ion,分娩前的預兆分娩啟動決定分娩過程的要素分娩過程接產(chǎn)產(chǎn)后期誘導分娩,2024/3/26,7,2011,Ⅰ 分 娩 前 的 預 兆 Signs of Approaching Parturation,家畜一般在分娩前的2～3周，開始出現(xiàn)一些將要分娩的癥狀：軟產(chǎn)道 外陰腫脹、松軟、增大，皺襞展平，子宮頸亦開始松軟，并有產(chǎn)量粘稠的半透明液流出，主要由于Es及RLX作用引起骨盆韌帶 薦坐韌帶、薦髂韌帶馳緩、

7、松軟，使尾根兩側(cè)凹陷，觸壓柔軟，薦骨后端的活動性因而增大，Es及RLX作用的結(jié)果乳房 顯著增大(增大特別快)，乳頭腫脹，開始分泌膠樣乳汁，分娩前2～3天變?yōu)槌跞榍胰榉磕[脹更明顯，有的乳牛出現(xiàn)漏乳現(xiàn)象，成滴或成股流出，漏乳開始后數(shù)小時～1天即分娩。(綿羊)舉止異常、準備產(chǎn)褥 表現(xiàn)不安，有的孕畜食欲下降，排泄量少而次數(shù)增多，某些動物如豬、犬、兔等，有銜草做窩等表現(xiàn)，準備分娩，兔子甚至咬下自體的被毛墊于窩或籠子的一側(cè)。放牧母駱駝、

8、母牛、母羊等離群現(xiàn)象、尋找安靜的地方準備分娩,2024/3/26,8,2011,,2024/3/26,Early signs of lambing. Mucus from Vagina.,9,2011,,2024/3/26,Restless Prepartum ewe.,10,2011,Hormonal changes cause:,1.Final maturation of fetus2.Expansion of birth ca

9、nal3.Maternal behavior4.Synthesis and ejection of milk5.Initiation of uterine contractions6.Termination of pregnancy,Initiates parturitionand lung development,Cortisol - stimulates lung surfactant,Prolactin comp

10、letes finalmammary development and milk secretion,Fescue(牛茅草) toxicity problems:Ergot(麥角菌) causes inhibition ofprolactin release and thus milk production,2024/3/26,11,表面活性劑,2011,Significance of initial hormonal chang

11、es Progesterone - removes block on uterine contractions. Estrogen - makes uterus more responsive to induction of contractions i.e., more irritable and smooth

12、 muscle tissue stimulation.Events just Prior to Parturition: 1. Pelvic ligaments soften - Tail head sinks due to estrogens and relaxin. 2. Cervix softens and begins secreting stringy(線狀) mucus -

13、 estrogens and relaxin. .,,,,Allows myometrial muscle fibers to work together in bundles,Induction of oxytocin receptors,,,Increased water content in cervical tissue andcervical plug(子宮頸粘液塞) is removed,2024/3/26,12

14、,2011,3. Swelling of vulva. 4. Udder swells - fills with first milk and due to edema: 5. Fetus moves into proper position - resting on thorax, front feet and head facing the cervix,Collagenase (膠原酶)breaks dow

15、n collagen which also widens the pelvis,Prolactin, Estrogens and glucocorticoids,2024/3/26,13,2011,Signs of Approaching Parturition,Distended abdomenMammary development & milk secretionSwollen vulva and relaxed pel

16、vic ligamentsMucous dischargeRelentlessness and separation from groupLabor and Contractions,2024/3/26,14,2011,Physical Signs of Parturition,Swollen udderEnlarged or dropped abdominal areaSwollen vulvaSeparation fro

17、m other animalsSwollen or leaking teats(漏乳)Increased mucus dischargeNervousnessAppearance of water bag from the vulvaLoss of appetite,2024/3/26,15,2011,Signs of Parturition in Cattle,One week - mammary glands fill w

18、ith milk, tailhead ligaments relax, and you will see a waxing of teats. 12~24 hours - frequent defecation and urination (二便), anorexia(食欲), looking for young, makes a nest or seeks out an isolated area.,2024/3/26,蠟,16,2

19、011,Signs of Parturition,Distended (swollen) udderFluid from udder changes from a watery solution to the thick, milky colostrumMuscles in the rear(后軀部) begin to shrink(緊縮) and fall awayenlargement & swelling of th

20、e vulvaNervous & uneasy behaviorMuscular contractions as labor begins,2024/3/26,17,2011,Signs of Parturition in Sheep,Ten days before lambing the ewes teats become firm and full of milk, her vulva slackens松軟 and be

21、comes slightly swollen. Closer to lambing, the ewe's cervical seal passes from the vulva as a thick, creamy, white mucus. In the final stages prior to lambing, the ewe becomes anxious and uneasy and continually swi

22、tches交替 from a reclining斜臥 to a standing position.,2024/3/26,18,2011,Signs of Parturition in Horses,Two to six weeks before foaling the mares udder will swell Seven to ten days prior to foaling the muscles over the butt

23、ocks(臀) appear to shrink and the abdomen drops At four to six days before foaling the teats fill with milk Twelve to 24 hours before foaling wax appears on the end of the nipples(乳頭),2024/3/26,19,2011,,2024/3/26,20,201

24、1,Ⅱ 分 娩 啟 動Initiation of Parturation,啟動分娩的因素內(nèi)分泌因素胎兒內(nèi)分泌變化母體內(nèi)分泌的變化機械性因素神經(jīng)性因素免疫排斥作用啟動分娩的機理,2024/3/26,21,2011,Ⅱ 分 娩 啟 動Initiation of Parturation,啟動分娩的因素 主要是機械因素、激素、中樞神經(jīng)及胎兒因素等互相作用的結(jié)果內(nèi)分泌因素 胎兒及母體內(nèi)分泌機能變化對分娩發(fā)動很重要

25、胎兒內(nèi)分泌變化 胎兒的下丘腦-垂體-腎上腺軸系對于分娩的啟動起著決定性作用。分娩前，胎兒腎上腺皮質(zhì)激素分泌增加，進入母血(羊未孕1ng/ml，分娩前100~200ng/ml)，刺激胎盤及子宮產(chǎn)生Es和PGs---黃體溶解及抑制孕酮分泌---子宮收縮增強，胎動增強，同時反射性地引起OT分泌，最后OT與PG一起使子宮收縮，引起分娩，排出胎兒。如切除胎羔下丘腦、垂體及腎上腺，則懷孕期延長，若再給胎羔滴注ACTH或地塞米松則又能誘發(fā)分娩,2

26、024/3/26,22,2011,Fetal Surgery.,The fetus is positioned for adrenalectomy via the flank. The fetal membranes and edges of the uterine incision are sealed by clamping to minimize lost of fetal fluids.,Fetal Adrenalectomy.

27、Experimental bilateral fetal adrenalectomy at 120-days of gestation rendered the fetus incapable of initiating parturition. And the fetus continued to grow past term until delivered by cesarean section. The fetal membra

28、nes and edges of the uterine incision were sealed by clamping to minimize lost of fetal fluids.,23,Ⅱ 分 娩 啟 動Initiation of Parturation,母體內(nèi)分泌的變化孕酮P4：黃體和胎盤產(chǎn)生的P4，對于維持妊娠起著極其重要的作用，P4可使子宮肌細胞保持安靜，抑制子宮收縮，在妊娠期間還能對抗Es的作用并降低子宮對O

29、T的敏感性。到懷孕末期，P4減少，對OT的抑制解除，OT分泌增多，作用增強；對子宮收縮的抑制作用減弱，并使子宮對Es和OT敏感，子宮收縮能力增強。雌激素Es：隨懷孕期的增長，胎盤產(chǎn)生的Es逐漸增加，分娩前可達到最高峰，可引起的反應(yīng)：使OT、乙酰膽堿增多(可能是使OT酶、膽堿酯酶失活)，刺激催產(chǎn)素受體增加，使子宮對OT敏感，增強收縮能力；使子宮、骨盆韌帶含水分增多，變松軟；激發(fā)子宮PG分泌增多，使子宮收縮增強。松馳素RLX增多：懷孕末

30、期的胎盤、子宮、黃體產(chǎn)生增多，分娩后即消失(迅速減少)，使被Es致敏后的子宮頸、骨盆韌帶松馳變軟，在分娩時易于擴張，還可控制子宮收縮。,2024/3/26,24,2011,Ⅱ 分 娩 啟 動Initiation of Parturation,前列腺素PGs：分娩前子宮靜脈血中PGF2α大量增加，這和Es及胎兒腎上腺皮質(zhì)激素刺激有關(guān)。主要是由母體胎盤合成的。PG對分娩所起的作用為：對子宮肌有直接刺激作用，收縮增強；溶解黃體；解除孕酮

31、的抑制作用；刺激神經(jīng)垂體釋放OT催產(chǎn)素OT：丘腦下部分泌在垂體后葉貯存，胎體在臨產(chǎn)前也能釋放OT，OT在胎兒通過產(chǎn)道時才出現(xiàn)高峰，使子宮發(fā)生強烈收縮，因而可能不是啟動分娩的主要因素，但對分娩過程的正常進行有重要作用。 子宮對OT的敏感性隨孕期不同而異。懷孕早期，即使給予母體大劑量的OT，也不發(fā)生反應(yīng)(因OT酶分解)。至懷孕后期，因為OT酶逐漸消失，僅用少量OT即可引起子宮強烈收縮，試驗證明，懷孕末期子宮對OT的敏感性可增

32、大20倍，前面已談過臨產(chǎn)前，P4↓、E2↑，可激發(fā)OT的分泌及子宮對OT的敏感性。皮質(zhì)醇 與胎兒下丘腦-垂體-腎上腺軸系機能關(guān)系密切,2024/3/26,25,2011,Parturition and Hormones,Decreased progesterone levels.Estrogen, relaxin, prosaglandins, and oxytocin levels increase.Estrogen caus

33、es the birth canal to open.Oxytocin causes contractions.Relaxin relaxes the pelvic muscles and ligaments.Prostaglandins causes contractions, CL …Prolactin triggers引發(fā) milk production.,2024/3/26,26,2011,Ⅱ 分 娩 啟 動Initi

34、ation of Parturation,2024/3/26,27,2011,Ⅱ 分 娩 啟 動Initiation of Parturation,機械性因素 懷孕末期，胎兒發(fā)育成熟---子宮擴張及張力增加---壓迫胎盤，使一部分胎盤變性，胎盤循環(huán)受到影響→胎兒營養(yǎng)供應(yīng)受到影響，故使胎動逐漸增強，子宮內(nèi)壓力及胎動對子宮頸的壓迫及刺激增強，反射性地引起垂體后葉分泌的OT增多，使被Es致敏的子宮收縮。同時，也反射性地引起下丘

35、腦及外周神經(jīng)釋放神經(jīng)遞質(zhì)(去甲腎上腺素、乙酰膽堿)增加，亦可引起子宮收縮。神經(jīng)性因素 神經(jīng)系統(tǒng)對分娩過程具有調(diào)節(jié)作用。例如胎兒的前置部分對子宮頸及陰道發(fā)生刺激，就能通過神經(jīng)傳導使垂體釋放催產(chǎn)素，增強子宮收縮。一般分娩發(fā)生在夜間的許多，因夜間安靜，外界光線弱，故子宮分娩收縮的刺激就成為大腦反射活動調(diào)節(jié)的優(yōu)勢現(xiàn)象。免疫排斥作用 懷孕期母體免疫排斥作用被抑制，懷孕期滿時，母體的免疫物質(zhì)可通過變性的胎盤作用于胎兒，從而發(fā)生免疫排

36、斥作用。,28,2011,Ⅱ 分 娩 啟 動Initiation of Parturation,啟動分娩的機理 是各種因素共同作用的結(jié)果 胎兒的下丘腦-垂體-腎上腺軸系與分娩的啟動密切相關(guān)。分娩前胎兒垂體分泌大量的ACTH→腎上腺皮質(zhì)激素增多→胎盤,使子宮產(chǎn)生Es、PGs增加→P4減少，黃體消退；Es使骨盆韌帶及生殖道松軟、腫脹、弛緩，并對OT、PG敏感性增強---子宮收縮活動漸增，為分娩做好組織學基礎(chǔ)；在孕

37、末期，子宮、胎兒迅速增大、胎動增加、壓迫及刺激子宮頸反射性引起OT及中樞神經(jīng)遞質(zhì)(NE、乙酰膽堿)分泌增多，使子宮收縮漸增；此外，由于孕酮下降，胎盤屏障作用減弱，對母體的免疫排斥反應(yīng)的抑制解除，對分娩的啟動也有一定作用。,2024/3/26,29,2011,Ⅱ 分 娩 啟 動Initiation of Parturation,,2024/3/26,30,2011,腎上腺皮質(zhì)激素,,2024/3/26,31,2011,,2024/3

38、/26,32,,2011,Hormonal Changes that Control Parturition,,,,,,Time of parturition iscontrolled by maturation of the hypothalamus- pituitary-adrenal axis,CRF,Fetal anteriorpituitary gland,Stimulates oxytocin recepto

39、rin myometrium,,,Steps Fetal ACTH causes - Fetal Corticosteroids causes - Progesterone levels placental production or CL regression) - Production of Estrogens by placenta - PGF2a productio

40、n by uterus -,Pine-needle abortion incattle - cause by a corticosteroid-like product,Corticotropic ReleasingHormone,Infusion inducesparturition,FetalAdrenal,AdrenalcorticotropicHormone (ACTH),Removal Blocks Pa

41、rturition,Corticosteroid,Glucocorticoid,Estrogen(Increase),Progesterone(Decrease),ProstaglandinF2a(Increase),,Hypothalamus,,,,,,Redrawn from Liggins, G.C. 1969. In Foetal Autonomy,2024/3/26,33,2011,Mare,The day of p

42、arturition may occur through corticosteroidsbut the time (minute) of the day is regulated by the release of oxytocin from the mare.,2024/3/26,34,2011,Parturition,Estrogen in late pregnancy:Stimulates production of oxyt

43、ocin receptors in myometrium.Produces receptors for prostaglandins.Produces gap junctions between myometrium cells in uterus.Factors responsible for initiation of labor are incompletely understood.,2024/3/26,35,2011,P

44、arturition (continued),Insert fig. 20.52,DHEAS：硫酸脫氫表雄酮,2024/3/26,36,2011,脫氫表雄酮,Parturition (continued),Fetal adrenal cortex:Chain of events may be set in motion through CRH production.Fetal adrenal zone secretes DHEAS(

45、硫酸脫氫表雄酮), which travel from fetus and placenta.Uterine contractions:Oxytocin.Prostaglandins.,2024/3/26,37,2011,Ⅲ 決 定 分 娩 過 程 的 要 素THE FACTORS DETERMINATING THE DELIVERY,產(chǎn)道(Birth canal)軟產(chǎn)道 Soft Birthcanal硬產(chǎn)道 Bony

46、 Birthcanal胎兒與產(chǎn)道的關(guān)系胎向 Presentation胎位 Position胎勢 Pusture前置 Fetal Presentation(胎前露) Antelocation產(chǎn)力(Expulsive force, Forces of Delivery)陣縮 Rhythmical contraction or Uterine cont.努責 Straining or Abdomi

47、nal and Diaphragmatic muscles cont.,38,Ⅲ 決 定 分 娩 過 程 的 要 素THE FACTORS DETERMINATING THE DELIVERY,產(chǎn)道(Birth canal) 產(chǎn)道即分娩時胎兒在母體內(nèi)經(jīng)過的通道。產(chǎn)道是否正常，影響胎兒排出的難易。產(chǎn)道又包括軟產(chǎn)道及硬產(chǎn)道軟產(chǎn)道：包括子宮頸、陰道、陰道前庭及外陰。分娩前在Es及RLX的作用下，變得腫脹松軟、富有彈性，分娩時容易擴張

48、，使胎兒易于通過硬產(chǎn)道：即骨盆腔 Pelvis骨盆腔的構(gòu)造：由髂骨、坐骨、恥骨、薦椎及前三個尾椎構(gòu)成內(nèi)腔，薦坐韌帶及半膜肌構(gòu)成大部分骨盆腔側(cè)壁。 骨盆腔大小、形狀是影響分娩難易程度的很重要因素。 其大小決定于垂直徑(恥骨聯(lián)合前端向頂壁的垂線)及橫徑(坐骨上棘之間的距離)入口：是腹腔通骨盆腔的口，由薦骨翼、髂骨干及恥骨前緣形成。入口的薦恥徑(豎徑)、橫徑(上中下)及傾斜度決定入口的大小 入口大而圓、傾斜度大

49、、胎頭愈容易進入骨盆腔(因骼骨干前移，使骨盆頂后端 骨部亦向前移；故分娩時胎兒通過后端坐骨棘(最狹部)時，能向上擴張出口：上為第三尾椎二側(cè)薦坐韌帶及半膜肌起點(尾椎、坐骨結(jié)節(jié))及下為坐骨弓構(gòu)成 上下徑(豎徑、尾坐徑)； 橫徑,2024/3/26,39,2011,骨盆軸(Pelvic axis) 為通過骨盆腔中心的一條假想線，它代表胎兒身體(縱軸)通過骨盆腔所走的線路。骨盆軸愈短愈直，胎兒愈易通過。牛呈屈曲狀，分

50、娩時間較長；馬、羊、豬較直，時間短 母畜骨盆腔的特點：入口大而圓,傾斜度大,恥骨前緣薄,坐骨上棘及坐骨結(jié)節(jié)低,薦坐韌帶寬,骨盆橫徑大,骨盆底前部凹而后部平坦寬,坐骨弓寬,出口大,故有利于胎兒通過。各種母畜骨盆腔的特點母馬：入口近圓形,薦恥徑高(♂18.75、♀23~24),橫徑大(♂20、♀23~24),傾斜度大,入口骨盆腔垂直徑(♀在4薦椎、♂右2薦椎)、坐骨結(jié)節(jié)低、坐骨上棘較小、坐骨弓較寬(比♂寬1/3)、出口較寬

51、、坐骨棘中部橫徑較大(♂15、♀20)。骨盆軸近直線，故分娩較快母牛：入口長圓形,薦恥徑(22~25),橫徑小(18~20),垂直徑(入口處22),坐骨上棘很高,坐骨結(jié)節(jié)高厚,坐骨弓狹,薦坐韌帶較狹,骨盆底壁后部有隆起嵴,故出口小;骨盆軸呈曲折狀,故分娩較慢母羊、豬：骨盆腔較大，骨盆軸較平直，故分娩較容易,2024/3/26,Ⅲ 決 定 分 娩 過 程 的 要 素 THE FACTORS DETERMINATING THE DE

52、LIVERY,40,2011,Ⅲ 決 定 分 娩 過 程 的 要 素 THE FACTORS DETERMINATING THE DELIVERY,胎兒與產(chǎn)道的關(guān)系 分娩時胎兒在產(chǎn)道內(nèi)的狀態(tài)(位置關(guān)系)， 胎向、胎位、胎勢胎向(Presentation)：胎兒的方向，即胎兒身體縱軸與母體縱軸的關(guān)系，有三種情況，即：縱向(Longitudinal p.)：胎兒身體縱軸與母體縱軸方向到

53、一致。正生(Anterior p.) 倒生(Posterior p. )，橫向(Transverse p.)：胎兒橫臥于子宮內(nèi)，胎兒身體縱軸與母體縱軸水平交叉 背橫向Dorsotransverse p. 腹橫向 Ventrotransverse p.豎向(Vertical p.)：胎兒豎臥于子宮內(nèi)，即胎兒身體縱軸與母體縱軸垂直交叉 背豎向 Dorsovertical p.

54、 腹豎向(Ventrovertical p.) 縱向為正常的胎向 橫向和豎向都是異常胎向，可致難產(chǎn),41,Ⅲ 決 定 分 娩 過 程 的 要 素THE FACTORS DETERMINATING THE DELIVERY,胎位(Position)：胎兒的位置，即胎兒背部貼近母體某部的關(guān)系上胎位(Dorsal position，背薦位 Dorso-sacral p.)：胎兒背部在上，

55、靠近母體背部或薦部，伏臥，為正常胎位下胎位(Ventral position，背恥位Dorso-pubic p.)：胎兒背部在下，靠近母體的恥骨(腹部下壁)，仰臥，為異常胎位側(cè)胎位(Lateral position，背骼位Dorso-ilial P.)：胎兒背部位于一側(cè)，靠近母體左或右側(cè)腹壁(髂骨)，側(cè)臥，異常胎位,2024/3/26,42,2011,胎勢(Pusture)：胎兒的姿勢，即胎兒身體各部在子宮或產(chǎn)道內(nèi)是伸直的還是屈曲的

56、，胎勢不正是引起難產(chǎn)的主要原因前置(Fetal Presentation)：即胎兒某部分和產(chǎn)道的關(guān)系，哪一部分向著產(chǎn)道，就叫哪一部分前置，如頭前置、臀前置、后肢（軀）前置、腕部前置，坐骨前置（髖關(guān)節(jié)屈曲）等,2024/3/26,Ⅲ 決 定 分 娩 過 程 的 要 素 THE FACTORS DETERMINATING THE DELIVERY,43,2011,分娩前胎兒在子宮內(nèi)的正常狀態(tài)：馬：縱向、頭前置、下胎位、頭彎向胸部、四

57、肢彎曲牛、羊：縱向、頭前置、側(cè)胎位、頭彎向胸部、四肢彎曲豬：因是多胎，子宮角長，胎兒位置常不一致，但頭彎向胸部、四肢彎曲是一致的 分娩時，胎向、胎位、胎勢改變,2024/3/26,Ⅲ 決 定 分 娩 過 程 的 要 素 THE FACTORS DETERMINATING THE DELIVERY,44,2011,Ⅲ 決 定 分 娩 過 程 的 要 素,,2024/3/26,45,2011,產(chǎn)力(Expulsive for

58、ce, Forces of Delivery) 是分娩時母體將胎兒排出體外的力量，包括子宮的收縮(陣縮or宮縮)及腹壁肌肉和膈肌的收縮(努責) 陣縮(Rhythmical contraction or Uterine cont.)：是排出胎兒的主要動力。陣縮是子宮肌層有節(jié)律性的收縮而產(chǎn)生的，二次收縮之間有間歇期。分娩初期(開口期)每次收縮時間短，收縮力弱，而間歇長；至胎兒產(chǎn)出期(后期)則每次收縮持續(xù)期長，收縮力強，而間歇期短；胎

59、兒排出后，子宮仍有輕微收縮。努責(Straining or Abdominal cont.)：是腹壁肌及膈肌的收縮，在分娩產(chǎn)出期對排出胎兒起重要作用，當分娩時胎兒前置部分進入子宮頸時，反射性地引起腹壁肌及膈肌收縮，所以努責是在胎兒產(chǎn)出期才開始出現(xiàn)。起初收縮力弱，間歇期長，以后收縮力強，間歇期短。由于強大的陣縮及努責的協(xié)同作用，很快把胎兒排出體外。正常情況下，胎兒產(chǎn)出后，努責迅速減弱、消失 diaphragm diaphragm

60、aticmuscle,2024/3/26,Ⅲ 決 定 分 娩 過 程 的 要 素 THE FACTORS DETERMINATING THE DELIVERY,46,2011,LABOR FORCE(一) THE UTERINE CONTRACTIVE FORCE(二) ABDOMINAL AND DIAPHRAGMATIC MUSCLES CONTRACTIVE FORCESBIRTH CANAL(一) BONY BIRT

61、HCANAL(二) SOFT BIRTHCANALFETUS(一) LENGTH OF FETUS(二) PRESENTATION(三) ABNORMALITY OF FETUSPSYCHICAL FACTOR,Ⅲ 決 定 分 娩 過 程 的 要 素 THE FACTORS DETERMINATING THE DELIVERY,47,2011,Ⅳ 分 娩 過 程 Parturient Process,分娩是

62、從子宮開始收縮到胎衣完全排出的全過程，在單胎動物一般可分為三期。開口期Stage of Cervical Dilatation 子宮頸開口期 第一期The First Stage 產(chǎn)出期Stage of Fetus Expulsion 胎兒排出期 第二期The Second Stage 胎膜排出期Stage of Fetal Membrane Expulsion 第三期The Third Stage,20

63、24/3/26,48,2011,Stages of Labour,From a physiological point of view, parturition has been subdivided in four phases (Gibb et al 2006):Phase 0, comprising some 95% of gestation, with the myometrium more or less quiescent

64、 and with the cervix hard and unyielding.Phase 1, the activation phase, during which there is: rapid softening of the cervix and the myometrium prepares for contractions of CAPs as a result of the removal of inhibitory

65、 factors (such as progesterone, relaxin); an increase of uterotropic factors (such as prostaglandins, oestrogens); increased stretchability伸展性 of the uterine wall. Thus during this phase all the final endocrine events o

66、ccur by which the fetal initiating signals are translated into functional changes in the cervix and myometrium.,2024/3/26,49,CAPs: contraction-associated proteins,Stages of Labour,Phase 2, the stimulation phase, involve

67、s the first and second stages of labour and is characterized by increasing myometrial contractility (by sheep increases of prostaglandin and oxytocin release), dilatation of the cervix and expulsion of the fetus(es). Ph

68、ase 3, the afterbirth stage, expulsion of the fetal membranes in those species where they are expelled one or more hours after the fetus, and the start of uterine and cervical involution. More traditionally, and

69、 from a more practical point of view, the process of parturition has been divided into three separate stages referred to as ‘the stages of labour’. While it is convenient to consider the process in this way, it is import